text:
\section{Introduction}
\label{sec:intro}
Since the earliest time of the Internet, its underlying architecture has been based on packet-switching and host-to-host communications. The TCP/IP layered architecture employs the same view and provides an abstract host-to-host communication model to communication applications. It decouples what to communicate from how the communication is done. This basic design feature of the TCP/IP architecture was far-reaching, allowing the Internet to grow for almost four decades while adopting various features and yet maintaining high efficiency. However, in the recent past there has been a profound increase in Internet connectivity, and with the emergence of new Internet applications, the Internet semantics have changed from host centric to content centric. To satisfy the needs of emerging internet applications, the current TCP/IP Internet architecture has adopted several application layer solutions known as over-the-top (OTT) applications, such as content delivery network (CDN), web caching, and peer-to-peer networking~\cite{Ge13, Malatras15}. With the addition of numerous applications, the gap between the basic semantics of the current Internet architecture and its usage is bound to increase; in fact, the additions of new OTT applications are leading us towards a very complex Internet architecture, and are introducing challenges to achieving efficiency, security, and privacy at acceptable economical cost.

Further, Internet trends are shifting away from browsing information to online consuming and sharing all types of content, including user-generated contents. Hence, the most promising characteristic of the future Internet is ubiquitous content delivery. What is being communicated is becoming more important than who is communicating. In this perspective, information-centric networking (ICN) has emerged as a promising architecture for the Future Internet; recently, the ICN support for 5G use cases were specified by NGMN. ICN represents a paradigm shift from host-centric to content-centric services and from source-driven to receiver-driven approaches. In the ICN paradigm the network is in charge of doing the mapping between the requested content and where it can be found. To do so, a network level naming is used for identifying content objects, independent of their locations~\cite{Jacobson09,Ahlgren12,Zhang13}. This means that the ICN architecture decouples contents from the host at the network level and supports a temporary storage of contents at in-network caches.

In ICN, in-network caching is an integral part of the ICN service framework~\cite{Jin12}\cite{Bilal17Access}. The benefits of the ubiquitous caching in ICN are profound, but it also introduces a challenge to content security; especially, the protection of a private or confidential content is a challenging task.  The ICN enabled cache routers can store the content segments for future use; hence, the content is temporarily cached in few intermediate cache routers while it is being delivered to a consumer. If content requests traverse a cache router that holds a temporarily cached copy of that particular content segment, then the request is entertained locally without being routed towards the publisher. However, in ICN the publisher has no control over the content after injecting it in the network; in particular, if  a private or confidential content is protected insecurely, then any unauthorized consumer can acquire it from intermediate caches. Traditionally, the protection of the content against unauthorized access requires consumer authentication and involves the conventional end-to-end encryption. Consequently, when the content is encrypted with the authorized user's key, the in-network caching becomes ineffective in ICN.

In Figure~\ref{fig:1}, a publisher $P$ publishes two content objects $O_{j}$ and $O_{k}$. Further, two consumers $N_{A}$ and $N_{B}$ subscribe to access these protected contents $O_{j}$ and $O_{k}$. Furthermore, the object $O_{j}$ is published without encrypting, scrambling, or hashing the content name, while the object $O_{k}$ is published with encrypting, scrambling or hashing the content name to ensure its privacy. Assume that the consumer $N_{A}$ sent an interest packet $I_{A,j}$ encapsulating the access authorization information. In reply, based on the subscription information, if $N_{A}$ is a valid subscriber, the publisher $P$ encrypts the requested content segment $S_{0,j}$ with a consumer specific key and sends it to the consumer $N_{A}$. Based on the semantics of ICN and cache replacement schemes, the intermediate cache router $R_{5}$ stores the encrypted content segment $S_{0,j}$ for future use. Now lets suppose, the consumer $N_{B}$ requests the same content. If the meta-data of the encrypted stored packet is available to $R_{5}$, as in case of $O_{j}$, then the intermediate cache router $R_{5}$ will reply with the cached content $S_{0,j}$ to the consumer $N_{B}$. However, $N_{B}$ cannot decrypt the content segment $S_{0,j}$ as it was solely intended for $N_{A}$ and thus the payload is encrypted with the key known to $P$ and $N_{A}$. Contrarily, if the meta-data of the encrypted stored packet is unavailable to $R_{5}$, as in case of $O_{k}$, the interest packet $I_{B,k}$ will be forwarded to the publisher.

\begin{figure
\centering
\includegraphics[width=0.42\textwidth]{image1.jpg}
\caption{Ineffective caching in ICN with end-to-end encryption.}
\label{fig:1}
\end{figure}

This issue can be solved by encrypting each content segment with a key known to all subscribers. In this regard, this issue can be viewed as a group key agreement problem. However, even in the presence of a perfect key distribution protocol, the assurance of backward and forward secrecy requires complex operations since the publisher in ICN has no control over the content after injecting it in the network. Moreover, in conventional group key agreement protocols~\cite{Bilal17Cluster,Zhang18}, the hosts share a cryptographic key for secure communications, which are not well-suited for the content centric ICN paradigm.

For example, if an authorized consumer unsubscribes from the service, then to ensure the forward secrecy it is necessary to make sure that leaving consumer don't have access to future keys for the group; hence, the shared key should be updated. From this point onward, the publisher would encrypt new version of content with updated group keys.  To access the content which is already disseminated in network caches, the authorized consumers need to keep both keys for effective cache utilization.  As shown in Figure~\ref{fig:1}(b), at time $t_{1}$, the publisher $P$ publishes object $O_{j}$ and shared the encryption key $K_{1}$ with all authorized consumers $N_{A}$, $N_{B}$ and $N_{C}$. Let's assume at time $t_{2}$ consumer $N_{B}$ unsubscribe with publisher $P$. The publisher $P$ will issue a new key $K_{2}$. Further assume that before unsubscribe event the copies of segment $S_{0,j}$ and $S_{1,j}$ were already disseminated in ICN core network; now if a consumer $N_{A}$ or $N_{C}$ request object $O_{j}$, it may get $S_{0,j}$ and $S_{1,j}$ from cache router encrypted with $K_{1}$ and rest of the segments from publishers encrypted with $K_{2}$. Similarly, if a new authorized consumer subscribes for the service, then to ensure the backward secrecy the shared key should be updated, and previous group members need to keep both keys for effective cache utilization.  Imagine a highly dynamic group where the consumers subscribe or unsubscribe very frequently, it will trigger numerous leave and join events, which will invoke group key agreement protocols each time. For effective caching, all consumers would keep record of multiple keys. Moreover, an extra decision operation is required to select a proper key; associating a time stamp can solve the problem at the cost of group member synchronization. Hence, the conventional group key management cannot handle the access control problem in ICN for ensuring the effective caching.

In our proposed scheme, we shifted the central target of keying process from hosts to data itself, i.e., the segments of the published content are encrypted with symmetric cryptographic keys that are unique to each segment and versions. The solution is to encrypt each content segment with a uniquely assigned key known to all subscribers; which raises three fundamental questions. How does one ensure that only an authenticated subscribed consumer can access the content? How can the consumer verify the originality of the content; that is, do we still need self-certifying? Finally, and most importantly, how can encryption keys be distributed among all of the consumers for each content segment? We answered all these questions in this work.

Specifically, we propose a secure distribution of protected content (SDPC) scheme, which consists of two protocol suites, 1) the keying protocol suite and 2) the subscription and content access protocol suite. The keying protocol suite enables the consumer and publisher to share a chain of secret keys required to decrypt the segments of the published content, while the subscription and content access protocol suite ensures that only authorized consumers receive the secret key generation information.

The remainder of this paper is organized as follows. In Sections~\ref{sec:related} and~\ref{sec:SystemModel}, we summarize the related works and present the system model, respectively.  Section~\ref{sec:SDPC} describes SDPC with detailed discussions. Section~\ref{sec:SecurityAnalysis} presents an inclusive security analysis. In Section~\ref{sec:Performance}, we present the performance analysis of SDPC. Finally, we provide concluding remarks in Section~\ref{sec:Conclusion}.

\begin{figure*
\centering
\includegraphics[width=1\textwidth]{image2.jpg}
\caption{Illustration of a) system model and b) naming scheme used in SDPC.}
\label{fig:2}
\end{figure*}

\section{Related Works}
\label{sec:related}

Most existing access control schemes for secure contents are application specific or lack security strength. For example, in~\cite{Cho14}, the authors presented a scheme for protected contents using network coding as encryption. However, the scheme requires a private connection between the publisher and consumer to obtain the decoding matrix and missing data blocks. In~\cite{Xiaobin16}, the authors presented a security framework for the copyrighted video streaming in ICN based on linear random coding. It is proven that the linear random coding alone improves the performance of ICN~\cite{Bilal18System}. However in~\cite{Xiaobin16}, each video was encrypted with a large number of symmetric encryption keys, such that each video frame was encrypted with a unique symmetric encryption key. Since only authorized users who possessed the set of all keys could decrypt the video content, the distribution of a large number of keys for each video content can be an extra communication overhead.

 In earlier work~\cite{SMisra19}, the authors proposed a content access control scheme for ICN enabled wireless edge. The proposed one is an extension of ~\cite{SMisra13}, which employs the public-key based algorithm and shamir's secret sharing as a building block, named AccConF. To obtain a unique interpolating polynomial of shamir's scheme, AccConF espoused Lagrangian Interpolation technique. The calculation of Lagrangian Interpolation is a computationally expensive process. To reduce the client-side computational burden the publisher piggy backs an enabling block with each content, which encapsulates partially solved Lagrangian coefficients.

In work by ~\cite{Wood14}, an access control realized by a flexible secure content distribution architecture, which combins the proxy re-encryption and identity-based encryption mechanisms. The publisher generates a symmetric key and encrypt the content before dissemination. To access the content from in-network cache or directly from publisher, a consumer first sends a request to publisher to acquires the symmetric encryption key. Upon receiving the key request, the publisher validates and verifies the authenticity of consumer, and sends the symmetric key encapsulated in response message encrypted with consumer's identity. The proposed scheme eliminated the asymmetric encryption, but it is not clear that how the consumer's private identity could be known to the content provider.

In other work ~\cite{Qzheng15}, author proposed a content access control scheme based on proxy re-encryption. In proxy re-encryption the content is re-encrypted by an intermediate node. In proposed scheme the edge routers perform the content re-encryption. Upon receiving a content request, the publisher encrypts the data and a randomly generated key k1, using its public key. Upon receiving the content request, edge router generates a random key k2 encrypted by the publisher's public key and signed by the edge router. Edge router sends the encrypted k2 to publisher and appends the encrypted k2 with the content and dispatch it towards consumer. Meanwhile, the publisher verifies the authenticity of consumer, and generates the content decryption key K using K1, K2 and public key. Upon receiving K the consumer can decrypt the content.

In other work~\cite{Qli17}, the authors proposed a distributed information flow control mechanism (named MCAC) to enable secure access control for the published content. In MCAC, the requests and content objects are labeled with \{$h$, $n$, $d$, $p$\}. These labels classify the contents based on the security and privacy requirements, where the h-level signifies the highest protection level and enforces non-caching policy, the n-level enforces the 1-level caching policy, the d-level permits multi-level caching policy, and the p-level supports all reading policy. To administer the MCAC information flow, the intermediate routers require to implement a trust computing base (TCB), consists of three modules; trust storage module (TSM), trust labeling module (TLM), and trust enforcement module (TEM). TSM governs the process of cryptographic session key establishment between participating routers and other nodes. The session keys are used to attain the h-level security by encrypting highly confidential $h$ labeled contents. TLM checks the label value and instructs the operating system accordingly to take further actions. TEM performs the content forwarding process and is responsible for content reclassification, i.e., TEM can re-labels a content to the h-level if it was at the n-level to hide the content based on privacy policy of the publisher. MCAC does not provide any mechanism to authenticate participating entities, which makes MCAC vulnerable to various attack. Moreover, to enforce the h-level security and privacy protection, all MCAC enabled routers need to establish a cryptographic session key and need to encrypt/decrypt all the communication between routers, which severely effects the performance of MCAC\footnote{ To verify the protocol claims, we implemented MCAC in an automated security protocol analysis tool, Scyther~\cite{Cremers12}, and also discussed its performance in Sections~\ref{sec:SecurityAnalysis} and~\ref{sec:Performance}.}.

In another study~\cite{Mannes15}, the authors presented an access control scheme for the encrypted content in ICN, which is based on the efficient unidirectional proxy re-encryption (EU-PRE) proposed by~\cite{Chow10}. The proposed scheme, named efficient unidirectional re-encryption (EU-RE), simplifies EU-PRE by eliminating the need of proxies in the re-encryption operation. However, the EU-RE scheme is still based on asymmetric cryptography, which is not suitable for several resource constraint applications such as, IoT and sensor networks. Moreover, the authors made an assumption that the content provider behaves correctly, i.e., it does not distribute any private content or decryption rights to unauthorized users. However, this assumption falsifies the protocol claims defined in~\cite{Cremers06}, which means EU-RE is weak against several attacks.\footnote{To verify the protocol claims, we implemented EU-RE in an automated security protocol analysis tool, Scyther~\cite{Cremers12}, and presented the results in Section~\ref{sec:SecurityAnalysis}.}

\section{System model}
\label{sec:SystemModel}

The system model used throughout this work is shown in Figure~\ref{fig:2}(a). For concrete discussion and better understanding, in the rest of the article, we present SDPC for a particular ICN architecture, i.e., named data networking (NDN)~\cite{Jacobson09}. However, SDPC can be adopted for other ICN architectures without changing the core idea.

In NDN core networks, we introduce a new entity, designated subscription manager $M$. The subscription manager $M$ can be a module installed on the publisher or it could be an independent entity in the network. In this work we assume that subscription manager $M$ is an independent entity associated with multiple publishers. We also assume that there is a secret number $n_{S}^{i}$ associated with each valid subscriber (or consumer) $i$, which is registered with the subscription manager $M$. The registration could be made offline or online using a smart mechanism. The subscription manger $M$ stores the secret number $n_{S}^{i}$ in a hash table, which is a part of registration database, as shown in Figure~\ref{fig:2}(a). Note that being registered does not mean the consumer is entitled to access a certain protected content.  When a registered consumer is interested in a protected content, the consumer should first subscribe to the protected content, for instance, subscribing to a movie channel. In the first step, the consumer sends an interest request for the protected content along with the subscription request, and the publisher routes the request towards the subscription manager $M$. After that, the subscription manager $M$ authenticates the consumer $N_{A}$ and in response the publisher $P$ sends the encryption key generation information $KEY_{MSG}$. Using $KEY_{MSG}$ as a seed for a secure hash function, the consumer $N_{A}$ and the publisher $P$ can generate a chain of keys. Then, the publisher $P$ uses these keys to encrypt the segments of the published content; likewise, after acquiring $KEY_{MSG}$ the consumer $N_{A}$ generates the same keys to decrypt the segments of the published content.

To acquire $KEY_{MSG}$, the first interest packet sent by a consumer should reach the publisher. To avoid any cache hit, it is important the name of the content should be unique between the consumer and the publisher, yet it should identify the requested object. As shown in Figure~\ref{fig:2}(b), the name of the segment $0$, "korea.ac.kr/$\sim$fil/test.doc/\_v1/\_s0", is a variable length and in a human readable form. However, to avoid any cache hit the SDPC naming scheme adopts the name uniqueness, such that the name of first interest is unique between consumer and publisher. To, achieve the name uniqueness the consumer inserts the hash of the secret number $n_{S}^{i}$, and encrypts the content name with $K_{TS}^{i}$. Then, the name of the segment $0$ becomes "korea.ac.kr/$\sim$fil/$Hash \left( n_{S}^{i} \right)$/$E_{TS}^{i} \left( test.doc/ \_v1/ \_s0 \right)$". In this naming scheme the insertion of digest and encryption of naming part provides a consumer-publisher specific unique name and as a result the interest packet always reaches the publisher without any cache hit. Note that the usage of consumer name space is restricted for acquiring $KEY_{MSG}$ only, this gives provides prevention against DoS attacks.

After acquiring $KEY_{MSG}$ the consumer can access the rest of the segments by using a shared authoritative name space. The name for each segment includes a hash digest $Hash \left( KEY_{MSG} \right)$, and the object name is encrypted with a uniquely assigned key $K_{l}^{j}$, which is generated using $KEY_{MSG}$ for each segment $l$ of an object $O_{j}$. For example, the name for segment $\_ s1$ of object $O_{j}$ is given by "korea.ac.kr/$\sim$ fil/$ Hash \left( KEY_{MSG} \right)$/$E_{1}^{j} \left( test.doc/\_v1/ \_s1 \right)$". With the insertion of $Hash \left( KEY_{MSG} \right)$ and encryption of the naming part with keys generated using $KEY_{MSG}$,\ this naming scheme provides a shared authoritative name space for all authorized consumers and thus it enables an effective content caching.  Moreover, this naming scheme ensures the privacy, because the content name is invisible to outsider without any knowledge of $n_{S}^{i}$, $KEY_{MSG}$, and cryptographic keys $K_{TS}^{i}$ and $K_{l}^{j}$.

Let's suppose Figure~\ref{fig:2}(a), a consumer sends an interest packet $I_{A,i}$ utilizing the proposed naming scheme. Then, the packet will reach publisher without any cache hit. Let us say that protected content object $O_{i}$ is composed of $k$ segments of $ S= \{ S_{1,i}, S_{2,i} \ldots S_{k,i} \}$; further, the intermediate cache routers $R_{1}$ and $R_{2}$ have the copies of the protected content segments, represented by $S_{R1,i} \subseteq S$  and $S_{R2,i} \subseteq S$. If the consumer is a valid subscriber, the publisher sends the encryption key generation information $KEY_{MSG}$ to the consumer. After receiving the key generation information, the consumer can decrypt the content segments, which may be delivered directly from the intermediate cache router.

\section{Secure Distribution of Protected Content}
\label{sec:SDPC}

SDPC consists of two protocol suites: 1) the keying protocol suite and 2) the subscription and content access protocol suite. The keying protocol suite is comprised of a key generation protocol and a key agreement protocol for content protection. Likewise, the subscription and content access protocol further includes three protocols, one dealing with the consumer subscription and the other two dealing with access to the protected contents published by different publishers.

\subsection{Keying Protocol Suite}

In the keying protocol suite, the key generation protocol generates a commitment key using an irreversible function similar to the ones used in~\cite{Bilal17JCS} \cite{Bilal17patent}. The commitment key is further used to drive multiple keys; for instance, a chain of content segment encryption keys, a ticket encryption key, and a consumer associated symmetric key are derived from the commitment key.

The key generation mechanism for the content protection is shown in Figure~\ref{fig:3}(a). First, the publisher divides a large content into equal sized segments. For each protected content object $O_{j}$, the publisher generates a unique commitment key generator by using an irreversible one-way hash function $\zeta_{0}^{j}=H \left( T_{P}, O_{j} \right)$, where $T_{P}$ is the time of publishing and $O_{j}$ represents the content name and version\footnote{Each version of content object is encrypted with a separate chain of keys. It empowers the publisher to control version-based access.}. After that, the publisher generates a chain of key generators of the length $L=\frac{sizeof \left( O_{j} \right) }{segment size}$ by using an irreversible one-way function $\{ H \left(  \zeta _{0}^{j} \right) = \zeta _{1}^{j}, H \left(  \zeta _{1}^{j} \right) =\zeta _{2}^{j}, \ldots, H \left(  \zeta _{l-1}^{j} \right) = \zeta _{l}^{j} \}$. Each generator $\zeta$ in the chain is used by a function $g$ at a specific index location in the chain to derive a content segment encryption key. For instance, at index $k$, the function $g \left(  \zeta _{k}^{j} \right) =H \left(  \zeta _{k}^{j},K_{p} \right)$ generates the key $K_{k}^{j}$ used for encrypting the $k$th segment of the content object $O_{j}$, where $K_{p}$ is the public key of the publisher. The use of $K_{p}$, in symmetric key generation process, implicitly ensures the originality of the content, i.e., the content are still self-certifying with out use of expensive asymmetric encryption. For instance, very efficient public key algorithms, such as ECC~\cite{koyama91}, are almost three thousand times slower than symmetric key algorithms~\cite{Wong06} such as RC5~\cite{Rivest94}. The symmetric keys generated as a result of the SDPC keying protocol have the size of 256 bits. Hence, in the subsequent section on the authentication protocols, any symmetric encryption algorithms supporting the 256-bit key can be used, e.g., RC5/6~\cite{Rivest94}, Rijndael~\cite{DaemenAES}, and Twofish~\cite{SchneierTwo}.

\subsection{Subscription and Content Access Protocol suite}
When a consumer wants to subscribe to the protected content, the consumer gains an initial access using a subscription protocol (SubP). After SubP, the consumer can use a ticket to access multiple protected contents published by the publishers or managed by a third party.

\begin{figure*
\centering
\includegraphics[width=0.82 \paperwidth]{image3.jpg}
\caption{The SDPC protocol suite: (a) symmetric keys generation and admission with reference to segment number of protected content and (b) message exchange for SubP, APSub, and APSub3.}
\label{fig:3}
\end{figure*}

\subsubsection{Initial Access and Subscription Protocol (SubP)}

If a consumer $N_{i}$ wants to subscribe to the protected content (e.g., subscribing for a movie channel), $N_{i}$ first generates an encryption key $K_{TS}^i=H(K_p^j\oplus n_S^i)$, where $K_{p}^{j}$ is the public key of the publisher and $n_{S}^{i}$ is a secret number shared with the subscription manager $M$. SubP continues as follows:

\begin{enumerate}
	\item  As shown in \textbf{1} at Figure~\ref{fig:3}(b), $N_{i}$ injects a subscription interest packet  $I_{i}$ and the NDN core network forwards it to the publisher $P_{j}$. The interest packet encloses $n_{0}^{i}$ that is encrypted with the generated encryption key $K_{TS}^{i}$.

	\item  Upon receiving the request from $N_{i}$, $P_{j}$ forwards the request in conjunction with its identity and the challenge $n_{2}$ to the subscription manager $M$. Note that $P_{j}$ cannot decrypt the part of the interest packet which is encrypted with key $K_{TS}^{i}$ and registration number $n_{S}^{i}$ remains invisible to the publisher.

	\item  $M$ retrieves the profile of $N_{i}$ from the database. If $N_{i}$ is a legitimate consumer, $M$ generates the keys $K_{TS}^i=H(K_p^j\oplus n_S^i)$ and $K_{S}^{i}=H \left( T_{M}\oplus n_{S}^{i} \right)$, and sends $u_{0}=E_{TS}^{i} \left( n_{0}+1 \vert  \vert n_{1} \vert  \vert T_{k} \vert  \vert K_{s}^{i} \right)$ to $P_{j}$, where $T_{M}$ is the time of issuing the session key $K_{S}^{i}$. The message M3 includes a ticket $T_{k}=E_{P}^{j} \left( N_{i} \vert  \vert K_{s}^{i} \vert  \vert  profile \right)$, a challenge $n_{1}$ for $N_{i}$, and a challenge response for $P_{j}$. After that, $ P_{j}$ verifies the challenge response and stores $n_{1}$ to use it as a message authentication in M5 and M6. In addition, $P_{j}$ retrieves the profile and the session key $K_{s}^{i}$ from the ticket. Since ticket is encrypted with the public key of $P_{j}$, the consumer  $N_{i}$ cannot decrypt it, but can use it to subscribe to other contents published by $P_{j}$, without contacting the subscription manager $M$.

	\item  $P_{j}$ forwards $u_{0}$ to $N_{i}$ along with $ KEY_{MSG}=H \left(  \zeta _{0}^{j},K_{p} \right)$, which is required to decrypt the segments of the published content and also used as a content object identifier. After verification of a challenge $\left( n_{0}+1 \right)$, $N_{i}$ accepts $T_{k}$ and generates a key chain to decrypt the protected content. The generated key chain involves the public key of $P_{j}$, hence, the content is also self-certifying.

	\item  $P_{j}$ sends the challenge response $\left( n_{1}+1 \right)$ to $M$ for the confirmation of a successful protocol run. After challenge $\left( n_{1}+1 \right)$ confirmation, $P_{j}$ may optionally register $N_{i}$ in its own database. If $P_{j}$ does not receive any challenge response within a certain period of time, $P_{j}$ marks $T_{k}$ as a stolen ticket.
\end{enumerate}

In SubP, secure exchanges of $n_{0}$, $n_{1}$, and $n_{2}$ ensure the message authentication between the consumer and the subscription manger, between the subscription manger and the publisher, and between the publisher and subscription manger, respectively. Likewise, the message authentication between the consumer and publisher is established by the session key encryption and $n_{1}$.

\subsection{Content Access Protocols}
\subsubsection{Access Protocol after Subscription (APSub) }

When the consumer $N_{i}$ wishes to access some other protected contents published by the publisher $P_{j}$, $N_{i}$ sends an interest request for the protected content along with the ticket $T_{k}$ and APSub continues as follows.

\begin{enumerate}
	\item  As shown in \textbf{2} at Figure~\ref{fig:3}(b), $N_{i}$ injects a subscription interest packet, enclosing $Access_{req}=E_{S}^{i} \left( N_{i} \vert  \vert n_{0} \right)  \vert  \vert T_{k}$. The NDN core network forwards it to the publisher $P_{j}$. The publisher $P_{j}$ decrypts the ticket and verifies the sender's identity $N_{i}$  by retrieving $K_{s}^{i}$. If the value $N_{i}$ does not match, $P_{j}$  will ignore the request and otherwise proceed as follows.

	\item  $P_{j}$ sends a challenge response along with the new challenge encrypted with the session key $K_{s}^{i}$. $P_{j}$ also send $KEY_{MSG}$, which is required to decrypt the segments of the published content.

	\item  $N_{i}$ sends a challenge response $n_{1}$. If $P_{j}$ does not receive the challenge response within a certain period of time, $P_{j}$ marks $T_{k}$ as a stolen ticket.
\end{enumerate}

In APSub, the secure exchange of $n_{0}^{i}$ ensures the message authentication between the consumer and the publisher.

\subsubsection{Access Protocol after Subscription involving a Third Party (APSub3)}

Assume a consumer $N_{i}$ subscribed with $P_{i}$, which means it shares a session key $K_{s}^{i}$ with $P_{i}$ and holds a $T_{k}$  encrypted with public key of $P_{i}$. Now if $N_{i}$ wishes to access the protected contents published by a third-party content publisher $P_{j}$, APSub3 continues as follows.

\begin{enumerate}
	\item  As depicted in \textbf{3} at Figure~\ref{fig:3}(b), $N_{i}$ injects a subscription interest packet enclosing $Access_{req}=E_{S}^{i} \left( N_{i} \vert  \vert n_{0} \right) \vert  \vert T_{k}$ and the packet is forwarded to the publisher $P_{j}$.

	\item  Upon receiving the request from $N_{i}$, $P_{j}$ forwards the request in conjunction with its identity and the challenge $n_{2}$ to $M$. Note that $P_{j}$ cannot decrypt  $Access_{req}$ in the interest packet that is encrypted with the key $K_{s}^{i}$, which a shared session key between $N_{i}$ and $P_{i}$, which ensures the third-party content distributor cannot misuse the consumer secure information, such as profile and secret share number.

	\item $M$ retrieves the profile from $T_{k}$, and if $N_{i}$ is a legitimate consumer, $M$ generates the key $K_{TS}^i=H(K_p^j\oplus n_0)$, and sends $u_{0}=E_{S}^{i} \left( n_{0}+1 \vert  \vert n_{1} \vert  \vert KEY_{MSG} \right)$  to  $P_{j}$. The message M3 also includes the key  $K_{TS}^{i}$, a challenge $n_{1}$ for $N_{i}$, and the challenge response for $P_{j}$, which are encrypted with the public key $P_{j}$. After that, the publisher $P_{i}$ verifies the challenge response and stores $n_{1}$. Note that the ticket is encrypted with the public key of $P_{i}$. Therefore, $N_{i}$ and third-party publisher $P_{j}$ cannot decrypt it. Also, $ KEY_{MSG}$ is inaccessible to $P_{i}$, which ensures that the third-party content distributor cannot misuse the protected content.

	\item  $P_{j}$ forwards $u_{0} \vert  \vert E_{TS}^{i} \left( P_{j} \right)$  to $N_{i}$. After the verification of the challenge $\left( n_{0}+1 \right)$, $N_{i}$ generates $K_{TS}^i=H(K_p^j\oplus n_0)$  and sends the challenge response $\left( n_{1}+1 \right)$ to $P_{j}$. Now $ N_{i}$ can generate a key chain to decrypt the protected published content. Since the key chain is generated using the public key of $P_{i}$, the content is also self-certifying.

	\item  $P_{j}$ sends the challenge response $\left( n_{1}+1 \right)$ to $M$ for the confirmation of a successful protocol run.

	\item  After the challenge confirmation, $P_{j}$ closes the protocol run. If $P_{j}$ does not receive any challenge response within a certain period of time, $P_{j}$ marks $T_{k}$ as a stolen ticket.
\end{enumerate}

In SubP3, secure exchanges of $n_{0}$, $n_{1}$, and $n_{2}$ ensure the message authentication between the consumer and the subscription manger, between the subscription manger and the third-party publisher, and between the third-party publisher and subscription manger, respectively. Likewise, the message authentication between the consumer and the third-party publisher is established by a temporary session key $K_{TS}^{i}$ and $n_{1}$.

\section{Security Analysis}
\label{sec:SecurityAnalysis}

This section presents an inclusive security analysis, formal analysis using BAN logic~\cite{Burrows90}, and Scyther implementation results~\cite{Cremers12}.

\subsection{Naming based Attacks}

In NDN the objects are identified by a human readable naming system, which can lead to watchlist and sniffing attacks~\cite{Jakobsson17,Abdallah17,Klump10}.

In watchlist, an attacker who has control over communication links and cache routers, can delete or filter the content based on a predefined list of content objects. With the use of SDPC, the content is encrypted and invisible to the attacker. Recall that in NDN it is not obligation that a content object must carry an explicit content name, rather it can carry an implicit content identifier computed from the corresponding interest. This solution hides the object from the attacker. Let us reconsider the example in Figure~\ref{fig:2}(b). The first interest packet carries the name "korea.ac.kr/$\sim$fil/ \(Hash( \left( n_{S}^{i} \right) \) / \( E_{TS}^{i} \left( test.doc/ \_ v1/ \_ s0  \right)) \)"  beside the insertion of hash digest \(hash( \left( n_{S}^{i} \right) \),  the object name is encrypted with  \( K_{TS}^{i} \) .\  After acquiring  \( KEY_{MSG} \)  the name for \_s1 is then given by "korea.ac.kr/$\sim$fil/ \(  Hash \left( KEY_{MSG} \right)  \)  / \(  E_{1}^{j} \left( test.doc/ \_ v1/ \_ s1  \right)  \)". The attacker cannot get $KEY_{MSG}$, $n_{S}^{i}$, $ K_{TS}^{i}$, and $K_{l}^{j}$, and thus launching watchlist attack is not possible. Moreover, it completely hides the object name from the attacker, which ensures the privacy of the consumer.

Contrarily, in a sniffing attack the intruder does not have any list of pre-defined contents, rather it monitors the network and filters or eliminates the data if it contains some specified keywords. Such sniffing attack is not possible in SDPC, because the data is encrypted with the secret keys.

\subsection{DDoS Attacks}
The in-network caching makes NDN intrinsically resilient against distributed denial of service (DDoS) attacks~\cite{Wang18,Xin16}.  DDoS is a malicious attempt to disturb normal traffic to a server, for instance, multiple compromised systems send fake interest packets to a content publisher. Once the content is disseminated across network caches, the DDoS attack against a publisher depletes due to the on-path cache hits. However, assume somehow an attacker manages to flood all interests to a targeted publisher. With the use of SDPC, the total burden after a successful DDoS attack on the targeted publisher will remain insignificant.  This is because the subscription manager $M$ keeps the record of registered nodes in the hash table, which entries represent $K_{TS}^i=H(K_p^j\oplus n_0)$ session keys. Thus, in case of suspicion, the subscription manger in SDPC can identify fake requests by a hash table lookup with the complexity $O \left( 1 \right)$.

\subsection{Time Analysis Attack}
In NDN any cache node can store content segments. An intruder can guess that a particular content was requested by a user in particular vicinity by observing the request response time of a cached or uncached content. With the use of SDPC the payload is encrypted with one of the key derived from $KEY_{MSG}$ and the name of an object is identified by the digest and encrypted fields.  Since the intruder cannot acquire $KEY_{MSG}$ on time, it cannot create a valid request to launch a time analysis attack.

\subsection{Unauthorized Access}
SDPC allows the caches to store encrypted contents and to use a naming scheme unrecognizable to intruders. An intruder can access the content only after acquiring $KEY_{MSG}$. Since the delivery of $KEY_{MSG}$ in SDPC is achieved by handshake messages, where each message exchange contains an explicate (nonce challenge) or implicit (encryption key derived from nonce) message authentication; further each message is encrypted with $K_{TS}^i=H(K_p^j\oplus n_0)$, for unauthorized access an intruder needs to acquire $K_{TS}^i$.

\subsection{Traffic Monitoring Attack}
In traffic monitoring attack \cite{Tlau}, an intruder targets a consumer and tries to identity the requested contents. To launch a traffic monitoring attack the intruder takes control of edge router and observes all the requests send by the target consumer. However, in SDPC the content name is encrypted, which hides the object name from the attacker, consequently the traffic monitoring cannot reveal the identity of requested contents.

\subsection{Formal Analysis using BAN Logic}

BAN logic~\cite{Burrows90} is widely used for the formal analysis of security protocols, till recently\cite{frash16} \cite{Mahood18} . To verify the security of the SDPC protocol suite, it is sufficient to demonstrate the security of SubP since the rest protocols are extensions of SubP. The BAN logic analysis shows that SDPC is safe against large number of attacks. A detailed formal analysis of SDPC using BAN logic can be found in Appendix-I or at~\cite{SDPC_App} .

\subsection{Scyther Implementation Results}

Although BAN logic provides a foundation for the formal analysis of security protocols, a few attacks can be undetectable even with BAN logic~\cite{Nessett90}. However, the critical analysis of BAN-logic in~\cite{Nessett90} is based on usage of asymmetric cryptography, whereas SDPC utilizes symmetric cryptography. Furthermore, \cite{Nessett90} argue that BAN-logic methodology is faulty because it is assumed that physical security and administration do not suffer from the loss of messages by the underlying communication facility or because of host crashes. Owing to replication of contents across the network, in ICN this assumption has minor effect. Still, for the additional proof of the strength of the SDPC protocol suite, we implemented SDPC, EU-RE~\cite{Mannes15}, and MCAC~\cite{Qli17} in an automated security protocol analysis tool, Scyther~\cite{Cremers12}.

We considered four claims: 1) aliveness, 2) weak agreement, 3) non-injective agreement, and 4) non-injective synchronization~\cite{Cremers06}. These four claims are proven to be true for SDPC  by using BAN logic. In Scyther, a protocol is modeled as an exchange of messages among different participating roles.  For instance, in NDN-SDPC, the consumer and publisher are in the roles of initiator (I) and responder (R), respectively, whereas the subscription manger is in the role of a server (S). In EU-RE, the publisher acts both as a responder and  as a server (R{\_}S), whereas in MCAC the consumer and publisher are in the roles of I and R, respectively, whereas the 3rd party authenticator has the role of S. The Scyther tool integrates the authentication properties into the protocol specification as a claim event. We tested SDPC, MCAC, and EU-RE by employing the claims mentioned earlier, with the parameter settings given in Table~\ref{tab:3}.

\begin{table
\centering
\caption{Scyther tool parameter settings.}
\label{tab:3}
\begin{tabular}{c|c}\hline{\smallskip}
Parameter  &	Settings   \\ \hline \hline
Number of runs  & 1 to 3\\ \hline
Matching type  & Find all types of flaws\\ \hline
Search pruning  & Find all attacks\\ \hline
Number of patterns per claim  & 10\\ \hline
\noalign{\smallskip}
\end{tabular}
\end{table}

\begin{table*}[ht]
\caption{Scyther results for SDPC, MCAC, and EU-RE.}\label{tab:4}
\centering
\begin{tabular}{c|ccccccccccc}
\hline{\smallskip}
\multirow{1}{*}{{\bf Claims}} & \multicolumn{3}{C{1.5cm}}{\bf MCAC \cite{Qli17}}& \multicolumn{3}{C{1.5cm}}{\bf MCAC \cite{Qli17} auth.}& \multicolumn{2}{C{1.5cm}}{\bf EU-RE \cite{Mannes15}}& \multicolumn{3}{C{1.5cm}}{\bf NDN-SDPC }  \\ \hline \hline

& $I$ & $R$ & $S$ & $I$ & $R$ & $S$ & $I$ & $R_S$ & $I$ & $R$ & $S$  \\ \hline
Aliveness & N & N & N & Y & Y & Y & Y & Y & Y & Y & Y  \\ \hline
Weak Agreement & N & N & N & Y & Y & Y & N & Y & Y & Y & Y \\ \hline
Non-injective Agreement & N & N & N & Y & Y & Y & N & Y & Y & Y & Y \\ \hline
Non-injective Synchronization & N & N & N & Y & Y & Y & N & Y & Y & Y & Y \\ \hline
\end{tabular}
\begin{tabular}{@{}cc@{}}
\multicolumn{1}{p{\linewidth-2cm}}{\footnotesize \center{N = Protocol claim is not fulfilled; Y = Protocol claim is fulfilled}}
\end{tabular}
\end{table*}

The Scyther results are shown in Table~\ref{tab:4}. It is clear that SubP qualifies all of the protocol claims and no attacks were found. Consequently, for a large number of systems and scenarios, SDPC guarantees safety against a large number of known attacks such as impersonating, man-in-middle, and replay attacks. However, in EU-RE, the author made an assumption that the content provider behaves correctly, i.e., it does not distribute any private contents or decryption rights to unauthorized users, this assumption falsifies the protocol claims, which means EU-RE is weak against several attacks. The Scyther implementation shows that initiator fails to confirm claims 2, 3, and 4.

In MCAC, the TCB along with encrypted communication between routers provide strong security against man-in-middle attack; however, during the bootstrapping, the session key establishment is conducted by the Diffie-Hellman (DH) key distribution algorithm ~\cite{Merkle1978} without using a proper authentication procedure. Since the DH algorithm does not inherently provide authentication, it can be secure only if it is properly integrated with another authentication protocol. This weak link in MCAC makes it vulnerable to several attacks, even a man-in-middle attack could be possible if an intruder tempered the session key distribution procedure during bootstrapping process. Therefore, from Scyther implementation results, it can be seen that MCAC fails to qualify a signal claim; further, if we assume the DH key exchange protocol is integrated with an authentication protocol or bootstrap process is hidden from the intruder, then MCAC qualifies all the claims. The inclusion of the authentication process causes the extra processing burden only during the bootstrap process and can be ignored for the next steps in the protocol.

\section{Performance Evaluation}
\label{sec:Performance}

We consider a scale-free network of 200 cache nodes generated using the Barabási–Albert (BA) model, as shown in Figure~\ref{fig:4}, which connects the publisher and the consumer space. Each cache router has a static request routing table. Further, we assume five content publishers in the network. Each publisher has 100,000 secure content items, and a Zipf-distribution with a popularity distribution exponent $\alpha=0.7$ is used to determine the population of content items in the entire network.

\begin{figure
\centering
\includegraphics[width=0.5\textwidth]{image4.jpg}
\caption{Network setup for performance evaluation.}
\label{fig:4}
\end{figure}

To ensure quick dissemination of the contents in the network, the publishers are connected to the cache routers with the highest betweenness centrality score, it helps to bringing system in steady state in short time. Furthermore, 25 gateway cache routers are connected to the consumer space with a large number of consumers. At any given time, 400~500 consumers are subscribed with each publisher and thus the total number of consumers subscribed to five publishers varies between 2,000 and 2,500. The size of each content item is 1GB, which is divided into 10 segments, and the link capacity between two cache routers is 1 Gbps, Finally, least frequently and recently used (LFRU)~\cite{Bilal17Access} is used in the experiment as a content replacement scheme.

We implemented the network setup, as described above, in MATLAB and compared the performance of NDN-SDPC against MCAC, EU-RE, and native NDN for two scenarios, 1) using end-to-end encryption, which makes the caching ineffective, as discussed in Figure~\ref{fig:1}, and 2) enabling the caching with a conventional way of a shared group key~\cite{Bilal17Cluster}\cite{Zhang18}. In the scenario 2, the shared group key enables in-network caching, but the shared group key is unfeasible because the authorized consumers need to keep a large number of keys for effective cache utilization in highly dynamic environments. Moreover, extra decision operations are required to select a proper key and to determine the timing of key deletion. For simplicity, in the scenario 2, we only consider the computational and message complexity required to ensure backward and forward secrecy. The processing required to select an appropriate key on the consumer side is ignored. Further, the scenario 2 is simulated for different levels of dynamicity in the consumer space, by considering 5, 15, and 25 leave and join requests per unit time; representing cases 1, 2, and 3, respectively. This comparison is made in terms of average download time\footnote{The average download time is defined as the ratio of the total number of requests observed on all 25 cache routers to the time taken to receive all the requested contents at the gateway routers.}, publisher load\footnote{The publisher load is defined as the percentage of interests reached at publisher. High the publisher load implies low cache hit.}, and timeout interest ratio\footnote{The timeout interest ratio is defined as the percentage of interests timed out and re-transmitted.}.

\begin{figure
\centering
\includegraphics[width=0.5\textwidth]{image5L.jpg}
\caption{Average download delay at gateway-cache router.}
\label{fig:5}
\end{figure}

Figure~\ref{fig:5} shows the comparison of the average download time observed when each of the 25 gateway cache routers receives the requests that are generated by a Poisson distribution with a rate $\lambda_j^d=100$ req/s.  The results are considered for different cache sizes of 200 MB to 100 GB; further, in case of MCAC, it is considered that 20\% of contents are labelled as the h-level and 80\% as the d-level.\footnote{The existence of different levels of content impacts the overall performance of MCAC, as shown in Figure~\ref{fig:6}.} From Figure~\ref{fig:5}, it can be seen that NDN with SDPC outperforms  EU-RE and native NDN both in the scenarios 1 and 2. The performance of NDN in the scenario 2 degrades further with the increase in dynamicity of the consumer space. The performance results of EU-RE are interesting, for smaller cache size [200MB-1GB], the performance of EU-RE is very close to NDN-SDPC, and it outperforms native NDN both in the scenarios 1 and 2. However, the performance gap increases with the increase of the cache size, and it falls down below NDN in the scenario 2 with case 3. In Eu-RE, the key revocation and content version are not correlated, and this can be one of the reason of such performance degradation. For a large cache size, MCAC performs better than EU-RE and NDN in scenario 2 with cases 2 and 3; however, NDN-SDPC and NDN in scenario 2 with case 1 outperform the MCAC. As discussed earlier, MCAC enforces intermediate routers to implement TCB, which includes several operations and encryption/decryption process for the h-level and the n-level secure content, these extra operations introduce processing delay at intermediate routers, the performance of MCAC further decreases with increasing the number of h-level contents.

\begin{figure
\centering
\includegraphics[width=0.5\textwidth]{image6L.jpg}
\caption{ Average download delay for different numbers of h-level contents.}
\label{fig:6}
\end{figure}

Figure~\ref{fig:6} shows the comparison of average download time comparison between NDN, NDN-SDPC and MCAC, for different numbers of h-level contents ranging from 0 to 100\% of total traffic, with the fixed 1GB cache size. From Figure~\ref{fig:6}, it is clear that performance of MCAC degrades with increasing number of h-level content.  The performance degradation of MCAC with increasing the number of the h-level contents is quite obvious, because h-level contents require no caching policy; hence, all interest packets traverse to the publisher.

\begin{figure
\centering
\includegraphics[width=0.54\textwidth,height=8.5cm]{image7L.jpg}
\caption{ Publisher load for different cache sizes.}
\label{fig:7}
\end{figure}

Figure~\ref{fig:7} shows the comparison of publisher load. We considered the case-3 level dynamicity of consumer space for EU-RE, MCAC, and NDN-SDPC.  From Figure~\ref{fig:7}, it is evident that in NDN-SDPC the publisher load is 12 to 20\% lower than EU-RE; however, publisher load at MCAC is almost same as NDN-SDPC, but MCAC's load increases with increasing number of h-level contents. This also implies that NDN-SDPC has higher cache hit ratio.
\begin{figure
\centering
\includegraphics[width=0.54\textwidth,height=8.5cm]{image8L.jpg}
\caption{Timeout interest ratio for different cache sizes.}
\label{fig:8}
\end{figure}
Similarly, from Figure~\ref{fig:8}, it can be seen that EU-RE, NDN-SDPC and MCAC, with small numbers of h-level contents, suffer with lower number of time out interest packets. However, NDN-SDPC and MCAC with 20\% of h-level contents suffer 35 to 50\% less than EU-RE; however, this performance metric also shows that performance of MCAC reduces with increasing number of h-level contents. This also implies that in comparison to EU-RE and MCAC, the NDN-SDPC provides better cache diversity.

\section{Conclusion}
\label{sec:Conclusion}

For effective caching and access control of the protected content in ICN, we proposed a secure distribution of protected content (SDPC). The SDPC's keying protocol suite empowers the publisher and consumer to generate multiple symmetric encryption keys with the exchange of a single commitment key. Moreover, SDPC's subscription and content access protocol suite ensures that only authenticated users can acquire the respective key generation information for the requested content. Another important aspect of proposed scheme is the hybrid naming scheme, which provide privacy protection and deters the time analysis attack. The commitment key in SDPC is generated with the publisher's public key, along with other secret credentials, and thus allows the consumer to implicitly verify the originality of the published content. In other words, self-certifying is achieved with the symmetric key cryptography, which makes SDPC free from the expensive computation overhead problem incurred in public key algorithms~\cite{koyama91}. Consequently, we believe that the adaptation of SDPC can make NDN more feasible for resource-limited networks such as Internet of things (IoT), which is one of our future works.

\appendices

\section{BAN logic Analysis}
\label{sec:appendixA}
Three basic objects of BAN logic are principals, formula/statements, and encryption keys. The principals and the protocol participants are represented by symbols \( P \) and \( Q \), respectively. The formula/statements are symbolized by \( X \) and \( Y \), and represents the content of the message exchanged. The encryption keys are symbolized by \( K \) . The logical notations of BAN-logic analysis are given in Table~\ref{tab:1}, and Some primary BAN-logic postulates used in the analysis of SDPC are summarized in Table~\ref{tab:2}.

\begin{table
\centering
\caption{Logical notations of BAN-logic.}
\label{tab:1}
\begin{tabular}{>{\centering}m{1.6cm}|m{6cm}}\hline{\smallskip}
Notation & Description   \\ \hline \hline

 \( P\models X\)   & \(P \) believes  \( X \) , or  \( P  \) would be enabled to believe  \( X \); in conclusion,  \( P \)  can take  \( X  \) as true.\\
 \hline
 \( P \mathrel{<\!\!\!\cdot} X \)   &  \( P  \) received a message  \( X  \) and  \( P \)  can see the contents of the message and is capable of repeating  \( X \)             \\
 \hline
 \( P \vert  \sim X \)  &  \(P \) has sent a message including the statement  \( X \). However, the freshness of message is unknown.            \\
 \hline
 \( P \Longrightarrow X\)  &  \(P \) controls \( X \)  and should be trusted for formula/statement  \( X \).         \\
 \hline
\( \# \left( X \right)  \)    &  \(X \) is\ fresh, i.e., \( X  \) never sent by any principal before.              \\
\hline
\( P \overset{k}{\leftrightarrow}Q  \)   &   \(P \) and \( Q \)  shares a key  \( K \) for secure communications and  \( K \) is only known to  \( P \) ,  \( Q \).             \\
\hline
\(  \left( X \right) _{K}  \)   &   The statement  \( X \)  is encrypted by key $K$.            \\
\hline
\(  \left( X \right) _{Y}  \)   &     It stand for  $X$ combined with $Y$. $Y$ is anticipated to be secret and its implicit or explicit presence proves the identity of a principal who completes $(X)_Y$.           \\
\hline
\noalign{\smallskip}
\end{tabular}
\end{table}

\begin{table
\centering
\caption{Primary BAN-logic postulates.}
\label{tab:2}
\begin{tabular}{>{\centering}m{3.0cm}|m{4.5cm}}\hline{\smallskip}

Rule  &	Postulate   \\ \hline \hline
Message meaning rules  & $\frac{{P \models P\stackrel{K}{\longleftrightarrow}Q,P \mathrel{<\!\!\!\cdot} {{\left( X \right)}_K}}}{{P \models Q\mid  \sim X}},$ \newline
$\frac{{P \models P\stackrel{Y}{\longleftrightarrow}Q,P \mathrel{<\!\!\!\cdot} {{\left\{ X \right\}}_Y}}}{{P \models Q\mid  \sim X}}$ \\
 \hline
Nonce verification rule  & $\frac{{P \models \# \left( X \right),P \models Q\mid  \sim X}}{{P \models Q \models X}}$ \\
 \hline
Jurisdiction rule  & $\frac{{P \models Q \Rightarrow X,P \models Q \models X}}{{P \models X}}$\\
 \hline
Freshness rule  & $\frac{{P \models \# \left( X \right)}}{{P \models \left( {X,Y} \right)}}$\\
 \hline
Believe rule  & $\frac{{P \models Q \models \left( {X,Y} \right)}}{{P \models X,P \models Y}}$\\
 \hline
Session key rule  & $\frac{{P \models Q\# \left( X \right),P \models Q \models X}}{{P \models P \stackrel {K} {\longleftrightarrow} Q}}$\\
 \hline
\noalign{\smallskip}
\end{tabular}
\end{table}

The SubP protocol should achieve the following four goals that state that both the consumer and the publisher trust the encryption key $K_S^i$ for the secure exchange of $KEY_{MSG}$:

\begin{itemize}
	\item G1: ${P_j} \models \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right)$
	\item G2:${N_i} \models \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right)$
	\item G3: ${P_j} \models {N_i} \models \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right)$
	\item G4:${N_i} \models {P_j} \models \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right)$
\end{itemize}

To verify the above-mentioned goals, the first step of BAN logic is to convert the subject protocol in its idealized form. The idealization is a process to represent each message exchange in its intended semantics. In other words, the idealization is a process of converting each message exchange into a logical formula by using BAN symbols and notations. The idealizations of SubP are given below.

\begin{itemize}

	\item M1: ${N_i}\xleftrightarrow{Via\,P_j}M:{\left\{ {\left( {{n_0},{N_i}\mathop  \leftrightarrow \limits^{n_S^i} M} \right)} \right\}_{K_{TS}^i = H\left( {K_p^j \oplus n_S^i} \right)}}$
	\item M2: ${P_j} \to M:\left\{ {{n_2},ID{P_j}} \right\}$
	\item M3:
\begin{align*}
& M \to {P_j}\colon \\
&\Biggl\{
\biggl[ n_1, n_2, \Bigl(
  \textit{profile}, N_i,
  N_i(\xleftrightarrow{K_S^i})P_j,\\
  &\# \bigl( N_i(\xleftrightarrow{K_S^i}) P_j \bigr)
  \Bigr)_{\!K_{\!P}^j}
  \biggr]_{K_{\!P}^j}, \biggl[ n_0, n_1, \Bigl(
  \textit{profile}, N_i,\\
&  N_i(\xleftrightarrow{K_S^i})P_j,
  \# \bigl( N_i(\xleftrightarrow{K_S^i})P_j \bigr)
  \Bigr)_{\!K_{\!P}^j},\quad N_i(\xleftrightarrow{K_S^i})P_j,\\
&  \# \bigl( N_i(\xleftrightarrow{K_S^i})P_j \bigr),
  N_i\xleftrightarrow{n_S^i}M
  \biggr]_{K_{\mathit{TS}}^i = H(K_{\!P}^j \oplus n_S^i)}
\Biggr\}
\end{align*}

	\item M4:
\begin{align*}
& {P_j}\xleftrightarrow{Via\,M}{N_i}\colon \\
&\Biggl\{  \biggl[ n_0, n_1, \Bigl(   \textit{profile}, N_i,\\
&  N_i(\xleftrightarrow{K_S^i})P_j,  \# \bigl( N_i(\xleftrightarrow{K_S^i})P_j \bigr)
  \Bigr)_{\!K_{\!P}^j},\quad N_i(\xleftrightarrow{K_S^i})P_j,\\
&  \# \bigl( N_i(\xleftrightarrow{K_S^i})P_j \bigr),  N_i\xleftrightarrow{n_S^i}M
  \biggr]_{K_{\mathit{TS}}^i = H(K_{\!P}^j \oplus n_S^i)}, \\
&\biggl[  \left\langle {\zeta _0^j,{K_p}} \right\rangle ,\quad N_i(\xleftrightarrow{K_S^i})P_j,\\
&  \# \bigl( N_i(\xleftrightarrow{K_S^i})P_j \bigr),  N_i\xleftrightarrow{n_S^i}M  \biggr]_{K_{\mathit{TS}}^i = H(K_{\!P}^j \oplus n_S^i)}
\Biggr\}
\end{align*}

	\item M5:${P_j} \to M:{\left( {{n_1}} \right)_{K_S^i}}$
	\item M6:${N_i} \to {P_j}:{\left( {{n_1}} \right)_{K_S^i}}$
\end{itemize}

In an idealized protocol narration of SubP, the messages clearly show all the assertions. Using these assertions, all the implicit assumptions can be explicit. Then, the initial assumptions of SubP are given below.

\begin{itemize}
	\item A1:$M \models \# \left( {{n_0}} \right)$
	\item A2:$M \models \# \left( {{n_2}} \right)$
	\item A3: ${P_j} \models \# \left( {{n_1}} \right)$
	\item A4: ${N_i} \models \# \left( {{n_1}} \right)$
	\item A5: ${N_i} \models \left( {{N_i}\xleftrightarrow{K_{TS}^i = H\left( {K_p^j \oplus n_S^i} \right)}M} \right)$
	\item A6: $M \models \left( {{N_i}\xleftrightarrow{K_{TS}^i = H\left( {K_p^j \oplus n_S^i} \right)}M} \right)$
	\item A7:${P_j} \models \left( {{P_j}\mathop  \leftrightarrow \limits^{K_P^j} M} \right)$
	\item A8:$M \models \left( {{P_j}\mathop  \leftrightarrow \limits^{K_P^j} M} \right)$
	\item A9: $M \models {N_i} \models \left( {{N_i}\xleftrightarrow{K_{TS}^i = H\left( {K_p^j \oplus n_S^i} \right)}M} \right)$
	\item A10: ${N_i} \models M \models \left( {{N_i}\xleftrightarrow{K_{TS}^i = H\left( {K_p^j \oplus n_S^i} \right)}M} \right)$
	\item A11: $M \models {P_j} \models \left( {{P_j}\mathop  \leftrightarrow \limits^{K_P^j} M} \right)$
	\item A12: ${P_j} \models M \models \left( {{P_j}\mathop  \leftrightarrow \limits^{K_P^j} M} \right)$
\end{itemize}

Let us analyze SDPC to show that $N_i$ and $P_j$ share a session key. From M1, we have
\begin{equation}\label{Eq1}
M \mathrel{<\!\!\!\cdot} {\left\{ {{n_0},\left( {{N_i}\mathop  \leftrightarrow \limits^{n_S^i} M} \right)} \right\}_{K_{TS}^i = H\left( {K_p^j \oplus n_S^i} \right)}}.
\end{equation}

\noindent A6 and the message meaning rule infer that
\begin{equation}\label{Eq2}
M \models {N_i}\mid  \sim \left\{ {{n_0},\left( {{N_i}\mathop  \leftrightarrow \limits^{n_S^i} M} \right)} \right\}.
\end{equation}

\noindent A1 and the freshness conjuncatenation comprehend that
\begin{equation}\label{Eq3}
M \models \# \left\{ {{n_0},\left( {{N_i}\mathop  \leftrightarrow \limits^{n_S^i} M} \right)} \right\}.
\end{equation}

\noindent Also, (\ref{Eq2}), (\ref{Eq3}), and the nonce verification rule deduce that
\begin{equation}\label{Eq4}
M \models \left\{ {{N_i} \models n_S^i,{n_0},\left( {{N_i}\mathop  \leftrightarrow \limits^{n_S^i} M} \right)} \right\}.
\end{equation}

\noindent Then, (\ref{Eq4}) and the believe rule infer that
\begin{equation}\label{Eq5}
M \models {N_i} \models \left( {{N_i}\mathop  \leftrightarrow \limits^{n_S^i} M} \right).
\end{equation}

\noindent From A2, (\ref{Eq5}), and the jurisdiction rule, it can be concluded
\begin{equation}\label{Eq6}
M \models \left( {{N_i}\mathop  \leftrightarrow \limits^{n_S^i} M} \right).
\end{equation}

\noindent This belief confirms that $M$ has received a message from a legitimate $N_i$. A2, A1, (\ref{Eq3}), and the freshness conjuncatenation comprehend that
\begin{equation}\label{Eq7}
M \models \# \left\{ {{n_0},{n_2},\left( {{N_i}\mathop  \leftrightarrow \limits^{n_S^i} M} \right)} \right\}.
\end{equation}

According to the nonce freshness, (\ref{Eq7}) proves that $M$ confirmed that $N_i$ is recently alive and running the protocol. Further, from (\ref{Eq4}) and (\ref{Eq7}), $M$ has guaranteed that the $N_i$ has been running the protocol, apparently with $M$. This also proves that $M$ and $N_i$ agree on the nonce values corresponding to all the nonce in M1 and M2. These three proven claims are known as aliveness, weak agreement, and non-injective agreement and defined in \cite{ Cremers06,Cremers12}.

From M3, we have
\begin{equation}\label{Eq8}
{P_j} \mathrel{<\!\!\!\cdot} {\left( {{n_1},{n_2},{{\left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j},\# \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right),n_0^i} \right)}_{K_P^j}}} \right)_{K_P^j}}.
\end{equation}

\noindent A7, (\ref{Eq8}), and $n_2$ nonce verification rule deduce that
\begin{equation}\label{Eq9}
{P_j} \models M\mid  \sim \left\{ {{n_1},n_0^i,{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j},\# \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right)} \right\}.
\end{equation}

\noindent In addition, A3, (\ref{Eq9}), and the freshness conjuncatenation comprehend that
\begin{equation}\label{Eq10}
{P_j} \models \# \left\{ {{n_1},n_0^i,{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j},\# \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right)} \right\}.
\end{equation}

\noindent (\ref{Eq9}), (\ref{Eq10}), and the nonce verification rule infer that
\begin{equation}\label{Eq11}
{P_j} \models M \models \left\{ {{n_1},n_0^i,{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j},\# \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right)} \right\}.
\end{equation}

\noindent (\ref{Eq11}) and the believe rule comprehend that
\begin{equation}\label{Eq12}
{P_j} \models M \models \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right).
\end{equation}

The logic belief proves that $P_j$ is confident and believes that $K_S^i$ is issued by $M$; moreover, the freshness of the key from (\ref{Eq10}) also suggests that $M$ is alive and running the protocol with $P_j$ and $N_i$. Further, from (\ref{Eq9}), (\ref{Eq10}), and (\ref{Eq11}), $P_j$ has guaranteed that $M$ has been running the protocol, apparently with $P_j$. This also proves that $M$ and $P_j$ are also agree on the nonce values corresponding to all the nonce in M3. This concludes that $M$ and $P_j$ also satisfy the liveness, weak agreement, and non-injective agreement. Consequently, (\ref{Eq11}), (\ref{Eq12}), and the jurisdiction rule conclude G1, i.e.,
\begin{equation}\label{Eq13}
{P_j} \models \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right).
\end{equation}

\noindent  From M4, we have
\begin{equation}\label{Eq14}
{N_i} \mathrel{<\!\!\!\cdot} {\left\{ {{n_1},{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j},\# \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right),{N_i}\mathop  \leftrightarrow \limits^{n_S^i} M} \right\}_{K_{TS}^i = H\left( {K_p^j \oplus n_S^i} \right)}}.
\end{equation}

\noindent (\ref{Eq14}), A5, and the message meaning rule comprehend that
\begin{equation}\label{Eq15}
{N_i} \models M\mid  \sim \left\{ {{n_1},{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j},\# \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right)} \right\}.
\end{equation}

\noindent Then, ({Eq15}), A4, and the freshness conjuncatenation rule infer that
\begin{equation}\label{Eq16}
{N_i} \models \# \left\{ {{n_1},{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j},\# \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right)} \right\}.
\end{equation}

\noindent (\ref{Eq15}), (\ref{Eq16}), and the nonce verification rule deduce that
\begin{equation}\label{Eq17}
{N_i} \models M \models \left\{ {{n_1},,{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j},\# \left( {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right)} \right\}.
\end{equation}

\noindent Then, (\ref{Eq17}) and the believe rule infer that
\begin{equation}\label{Eq18}
{N_i} \models M \models \left\{ {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right\}.
\end{equation}

The logic belief proves that $N_i$ is confident and believes that $K_S^i$ is issued by $M$; moreover, the freshness of the key from (\ref{Eq16}) also suggests that $M$ is alive and running the protocol with $N_i$. Further, from (\ref{Eq15}), (\ref{Eq16}) and (\ref{Eq17}), $N_i$ has guaranteed that $M$ has been running the protocol, apparently with $N_i$ and $P_j$. This also proves that $M$ and $N_i$ are also agree on the nonce values corresponding to all the nonce in M4. This concludes that $M$ and $N_i$ also satisfies the liveness, weak agreement, and non-injective agreement. Conseuqently, (\ref{Eq17}), (\ref{Eq18}) and the jurisdiction rule conclude G2, i.e.,
\begin{equation}\label{Eq19}
{N_i} \models \left\{ {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right\}.
\end{equation}

From M5, we have
\begin{equation}\label{Eq20}
{N_i} \mathrel{<\!\!\!\cdot} ID{S_j}.
\end{equation}

\noindent (\ref{Eq13}), (\ref{Eq19}), (\ref{Eq20}), and the meaning rule comprehend G3, i.e.,
\begin{equation}\label{Eq21}
{P_j} \models {N_i} \models \left\{ {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right\}.
\end{equation}

From M6, we have
\begin{equation}\label{Eq22}
{P_j} \mathrel{<\!\!\!\cdot} {n_1}.
\end{equation}

\noindent (\ref{Eq13}), (\ref{Eq19}), (\ref{Eq21}) and nonce verification rule deduce G4 of
\begin{equation}\label{Eq23}
{N_i} \models {P_j} \models \left\{ {{N_i}\mathop  \leftrightarrow \limits^{K_S^i} {P_j}} \right\}.
\end{equation}

The logic belief proves that $N_i$ is confident and $P_j$ also believes that $K_S^i$ is issued by $M$. Moreover, (\ref{Eq5}), (\ref{Eq11}), and (\ref{Eq17}) prove that all communicating partners are confident that their communication partners exactly follow their roles in the protocol and exchange the intended messages in the intended order. This proven claim is known as non-injective synchronization and defined in~\cite{Cremers06}.

redpajama_set_name: RedPajamaArXiv


When most people hear the word "Smithsonian," they think of the museums lining the National Mall or maybe the National Zoo. But the Smithsonian is also a global institution working on projects around the world, from saving endangered species to safeguarding priceless artifacts.
For nearly a decade, one project in particular has been taking Smithsonian Exhibits' graphics supervisor, Scott Schmidt, more than 7,000 miles away from Washington, D.C., to monasteries in India. It's called Science for Monks and Nuns.
This unique program began in 2001 as a way of creating a dialogue between Western science and Tibetan Buddhism—something the Dalai Lama (the spiritual leader of Tibet) has long encouraged.
Every year, Science for Monks and Nuns brings Western scientists to India to engage monks and nuns (known collectively as monastics) in hands-on workshops on a variety of topics, including biology, neurology, cosmology, math, and physics. After the workshops, the monastics return to their communities to share what they have learned and continue their studies. In 2009, the group began creating exhibits as another way of sharing what they have learned with others.
Scott leads Monks in an exhibit design workshop in Bir, India.
Scott got involved in the project in 2010 through a request from the Smithsonian Center for Learning and Digital Access. Since then, he has used his exhibit skills to provide training and assist the group with planning and developing exhibits. In addition to the Smithsonian Institution, Science for Monks and Nuns partners with the Exploratorium in San Francisco and several universities in the United States.
Over the years, Scott and his colleagues have helped create two major science exhibits that have traveled throughout India, Nepal, and Bhutan; facilitated workshops and training sessions; and consulted on the creation of permanent science centers and "tinker spaces" at monasteries. A tinker space is a space with tools to build structures and prototypes demonstrating scientific phenomena, which are used in the workshops and exhibits.
Scott leads a training session in tool use and exhibit assembly at the science center in Dharamsala, India.
The first exhibit Scott worked on, The World of Your Senses, explored parallel Western and Buddhist perspectives on the five senses.
Scott speaks to colleagues during the production of The World of Your Senses exhibit.
The exhibits are truly cross-cultural, combining elements of both Western and Tibetan philosophy and design. For The World of Your Senses, the monks decided that the panels should be painted like thangkas, a traditional Tibetan style of religious paintings.
Scott and his colleagues discuss a tailoring detail for The World of Your Senses exhibit. The master tailor to His Holiness the Dalai Lama, Phuntsok Tsering, led the framing and sewing of the completed paintings.
A monk leads a tour of The World of Your Senses exhibit.
Monastics visit The World of Your Senses exhibit in Nepal.
The second exhibit Scott worked on, My Earth, My Responsibility, focused on climate change.
Scott and his colleagues examine mock-ups of the My Earth, My Responsibility exhibit.
The Dalai Lama attends the opening of the My Earth, My Responsibility exhibit at the Sera Jey Science Center in India. Pictured on the right is Ven. Geshe Lhakdor, Director of the Library of Tibetan Works and Archives, the organization that facilitates the Science for Monks and Nuns program.
Scott (right) meets the Dalai Lama at the opening of the My Earth, My Responsibility exhibit at the Sera Jey Science Center in India.
The work that goes into these exhibits is intense. Scott and his colleagues spend weeks at a time in India, working with the participants to plan, develop, and fabricate the exhibits.
One of the biggest challenges is translating complex scientific and metaphysical concepts into a few paragraphs of English and Tibetan text. "It can difficult to communicate concepts and words for which there may be no Tibetan equivalents," says Scott. However, with the help of monastics and a great team of interpreters at the Library for Tibetan Works and Archives, this challenge has not been a roadblock.
Throughout the six visits Scott has made to India so far to work with the program, he has come away inspired, renewed, and with new insights to bring back to his everyday life. "Collaborating with colleagues Tracie Spinale, Stephanie Norby, and Darren Milligan at the Smithsonian Center for Learning and Digital Access has been wonderful," says Scott, "and watching the program and monastic students develop since that first exhibit in 2010 has been a joy.
All photos by Bryce Johnson unless otherwise noted.
The Universe in a Single Atom by His Holiness the Dalai Lama, great for understanding his love of science and its positive effect on Buddhism.
Thanks to former SIE intern Elizabeth Polvere for her help in developing this blog post.
Sometimes small artifacts can have outsized meanings. Take the dog tags in the National Museum of American History's (NMAH) new exhibit Many Voices, One Nation, which explores how the many voices of people in America have shaped our nation. The dog tags belonged to men and women of different ethnicities and faiths who served in the armed forces in the 1940s and '50s. The original artifacts measure only a couple of inches wide, but they speak volumes about the diverse Americans who risked their lives to serve their country.
As part of the exhibit, NMAH asked Smithsonian Exhibits (SIE) to create touchable replicas of eight dog tags, enlarged to twice their size to reveal details. Model maker Chris Hollshwander led the effort for SIE.
The first step was to stitch together a series of high-resolution photos of the dog tags taken from different angles, using a process known as photogrammetry, to create 3D polygon models. This was a challenge because the reflective surface of the dog tags distorted some of the details, which had to be cleaned up using digital sculpting software.
Once the digital 3D models were complete, Chris programmed the computer numerical control (CNC) milling machine, to cut the replica dog tags out of aluminum.
Chris used CAM (computer-aided machining) software to create toolpaths for the CNC milling machine.
The replica dog tags are cut out of aluminum using the CNC milling machine.
The original dog tags are worn from combat and years of age. To recreate this appearance as closely as possible, Chris sandblasted the replicas, polished them on a buffing wheel, and used shades of black and brown paint to darken the letters and mimic the dirt, oils, and scratches on the originals. He then covered them with a coat of urethane to protect them from further wear and tear from visitors' hands.
A detailed view of one of the replica dog tags shows the wear and tear added to mimic the original artifact.
Once the dog tags were ready, it was time to install.
Chris lays out the replica dog tags to determine their placement on the panel.
Chris uses screws to secure the replica dog tags to the panel.
Chris fits the panel into place in the exhibit.
The finished product is ready for show time.
Visitors get hands-on with the replicas.
Every year, Smithsonian Exhibits (SIE) develops, designs, and builds many exhibits on the National Mall in Washington, D.C. But sometimes our work takes us farther afield. Recently, SIE exhibits specialist Zach Hudson traveled more than 5,000 miles to Benin City, Nigeria, for the Smithsonian's National Museum of African Art (NMAfA), to assist with training staff and installing an exhibit at the National Museum of Benin. Zach captured the photos shown here using a GoPro camera.
The National Museum of Benin was recently renovated and its exhibits are in the process of being rebuilt. Zach helped install a traveling version of the exhibit Chief S.O. Alonge: Photographer to the Royal Court of Benin, Nigeria. The exhibit was originally organized and produced by NMAfA, where it was on display from 2014 to 2016. It showcases the photography of S.O. Alonge, who served as the official photographer to the Royal Court of Benin for fifty years and also owned and operated his own photo studio.
A panel from the original exhibit at NMAfA. Photograph by Franko Khoury, National Museum of African Art, Smithsonian Institution.
Self-portrait of photographer S.O. Alonge, ca. 1942. Chief S.O. Alonge Collection, National Museum of African Art, Smithsonian Institution.
A portrait of Stella Osarhiere Gbinigie at age 15 by S.O. Alonge, ca. 1950. Chief S.O. Alonge Collection, National Museum of African Art, Smithsonian Institution.
Many of Alonge's photos are in the NMAfA's archives and NMAfA's chief archivist Amy Staples helped organize the exhibit and accompanied Zach to Nigeria. SIE senior exhibit designer Paula Millet traveled to the museum last year to help plan the exhibit. You can read about her trip on our blog here.
NMAfA chief archivist Amy Staples (seated at left) and SIE exhibits specialist Zach Hudson (seated at right) pose with the staff of the National Museum of Benin, including assistant director and curator Theophilus Umogbai (seated at center).
In addition to photographs, the exhibit features three-dimensional artifacts, including several Benin bronzes — traditional bronze sculptures from the kingdom of Benin, one of Africa's oldest and most highly developed states. Before leaving for Nigeria, Zach designed and made mounts for the artifacts. He used photos and design drawings for reference, since the objects were already in Nigeria. All the tools and materials Zach brought with him had to break down and fit into a single checked bag. This required meticulous packing skills.
Zach spent two days training the museum's staff in how to use tools for installation and fit mounts to artifacts. The staff practiced these skills as they installed the exhibit.
Zach trains museum staff members in tool usage.
Museum staff members practice their skills while working on the exhibit.
Zach discusses mount making with museum staff members.
Zach watches as museum staff members install exhibit panels featuring Alonge's photos.
While in Nigeria, Amy and Zach visited members of the local community, Benin Royal Court, and the Edo State Government. Zach had researched the kingdom of Benin, its culture, and traditions to prepare for his trip. Local residents were thrilled to have the exhibit in Nigeria and to be able to display Alonge's images in the place they were made.
The exhibit is scheduled to open at the National Museum of Benin on September 29.
Have you ever visited a museum and seen a sign that says, "Do not touch"? Sometimes museums have a reputation for being hands-off places, but we seek to change that. Smithsonian Exhibits (SIE) specializes in creating 3D tactile versions of artifacts. These durable replicas allow visitors to get up close and personal with priceless objects, something you could never do otherwise. They can enlarge and reveal key details of artifacts that are not clearly visible and make exhibits more accessible to visitors with visual impairments.
Recently, SIE worked with the Smithsonian's National Museum of American History to develop a replica of an ivory and gold cane head that belonged to former president John Quincy Adams for the exhibit American Democracy: A Great Leap of Faith. The exhibit traces America's unfolding experiment with democracy, from the American Revolution to today.
John Quincy Adams's cane is featured in the exhibit American Democracy: A Great Leap of Faith. Photograph courtesy of Division of Political History, National Museum of American History, Smithsonian Institution.
SIE staff used detailed photos of John Quincy Adams's cane, such as this one, to create the replica.
As with most of SIE's projects, this was a team effort. SIE model maker Chris Hollshwander used a series of detailed photos to create a three-dimensional computer model of the cane head. SIE model maker Carolyn Thome then used the digital sculpting process to recreate the intricate details on the gold-inlaid eagle.
Chris used computer-aided machining (CAM) software to create tool paths to drive a computer numerical control (CNC) milling machine. He used these tools to cut a master pattern of the cane head in polyurethane and a prototype of the eagle in polyurethane board.
The polyurethane pattern, on the right, was used to create a mold for the final replica.
Once the pattern was created, a silicone mold was made to cast a replica in resin. One of the most challenging parts of this project was matching the tint of the resin to the original ivory. Chris had to experiment several times to get the color right.
The replica eagle is cut out of a brass plate.
Once the prototype was approved, the replica eagle was cut out of brass and fitted into place for the final detailing. We think you'll agree that the result is spectacular!
The final replica is prepared for installation.
The replica is mounted on a plinth and ready to be touched.


There are three achievements for the arcade mode, when finish it with all silver, all gold and all platinum and of course the easiest one gives you the most gamerscore.
Getting silver medals is fairly easy, gold medals are more of a challenge but the platinum ones are the most difficult ones.
I will try to guide through the ten chapters and give you some tips, so here we go.
Choice of the car or bike: Is very essential, there are some dominating cars and most of the time cars are far better than bikes. You can check the leader board for each specific track and I will also recommend a car for you.
Of course try to race as fast as you can, so that you are familiar with the tracks and the cars.
Try to avoid style kudos in any races where they are not necessary, it will only slow you down.
Always try to get in the first place as soon as possible, it is a big advantage if you are the leading one.
Take down your opponents whenever you can, use them instead of your own brakes.
Whenever you can, try to use slipstream.
Manual transmission is not necessary, if you can handle it well you are a bit faster but it is also possible to do without it.
When style kudos are necessary always use the handbrake to introduce a drift.
Be patient and have a bit of luck.
Just try to get the first place very soon so that you are able to defend it, if you are not in the first place soon you might just follow the mob but will never come closer. Try to take them out in the very first turn.
Avoid the last place, use the same technique given in the street races.
Is easier since there is only one enemy that you can take very easily just at the start.
Get as many kudo stars as possible, try to drift as often as you can but stop when you have five stars. Also keep in mind that you have to finish the race within time.
Kudos will stop the clock so drift as often as can, also on the straights. Just always from the left to right and from the right to the left. Also use burnouts when you are to slow.
Pass the gates fast, once you know the track this is easy but do not hit a single cone, you may restart then.
Hit as many cones as possible, always hit all the straight ones and drift in the corners so that you will hit many of the corner cones.
The radars are mostly just behind a turn, so you have to take that turn as good as you can, you may use the manual transmission here to get a little bit faster.
Hit as many checkpoints as possible before you run out of time. You have to race very fast here unfortunately there is nothing more to say here.
Overtake as many cars as possible, you can also use the other cars to take a turn very well.
Complete a lap within the demanded time, this will also require you to drive near perfection.
You should not have any problems here with that car, the AWD will give you an excellent start.
It is all about the style here, drift often, that is very easy with a bike, make wheelies and endos.
This is a very good car, so show your AWD dominance here, this ones is also easy.
This will be the last chapter where you should use bikes.
Use the Pontiac Firebird for the two cone sprint races and the MX-5 for the other races.
Now it will get more difficult, you may also choose a different car but the RUF RT12 is quite a nice car here.
Now with A-class cars the choice is difficult, but those two cars are greatly balanced, use the CLK-GTR for the tricky tracks and the F50 for the straight tracks, then you should do good after some tries.
With that car this chapter seems to be to easy, got all platinum within the very first attempt so I hope you also succeed with that.
Ok, this is the most difficult chapter due to the two races on the Behemoth.
You should use the F50 for the two elimination races and use the CLK-GTR for the other two races. Use the CLK-GTR on the first Nürburgring race, try to get in the first place very soon, use the first turns after the long straight to achieve that and then you try to finish the race clean, if you are familiar with this track you may succeed even with that rainy weather.
The race on the Behemoth is the most difficult race in the arcade mode, as it is the long version which will take about seven minutes and it is also backwards so that it is a completely new track to you. You have to be very patient here as you will try it several times, but each attempt will make you better. To choose a car here is very hard. After I have tested all possible cars I came to the conclusion that the RUF Supercar Concept is the best for that track. The handling seems to fit most for that track, so try to get right behind the two Ferraris after the first turn and use the slipstream to keep up to them. You should be able to overtake them in the following turns and then try to keep the leading. Easier said then done, but some time you will succeed.
This chapter is also not easy and will require you to drive perfect most of the time. Once again those cars are only a suggestion from me, you may also choose different ones, perhaps the Gallardo. So mind my tips and should also succeed here, use a car with insane difficulty on the time vs. kudos track. By the time you pass chapter nine with platinum you have finished the most difficult races already. So be patient and you will be rewarded with 40G for silver and 10G per gold and platinum.
So I hope that this solution will help at least a bit, nevertheless you have to do it all by yourself and it is not that easy.
There are currently no gaming sessions for the Silver Gotham Arcader achievements that you can join - why not register and make a new session?


The annual New Year's pie-cutting event of Generation Y - International Interactive Agency took place on Saturday, 5 March. The event was hosted at the beautifully illuminated Gazarte hall with special gifts and best wishes for a creative and productive year. Everyone was there and it was indeed a great opportunity for all staff members and corporate associates to relax and get to know each other even better.
Mr. Vasilis Rodokanakis, Chief Technology Officer of the company cut the New Year's pie, whereas the traditional ceremony was followed by inspirational speeches by himself and other division heads.
Moreover, Mr. Anastasios Spanidis, CEO of Generation Y, thanked all the attendees for their presence, set out the new goals and initiatives and made reference to growth, development and openness. From the agenda could not be skipped out the upgrade of the custom e-commerce platform, Generation NEXT.
During this memorable night, the Management Team and Dr. Giannis Kalogerakis offered awards to those employees, who attended and successfully completed the training seminar "Anthropocentric and Ethical Approach" throughout the course of 2015.
And what could be better than a grand finale filled with live music and dancing. The music band, composed by talented musicians, staff members of Generation Y, entertained the attendees and surprised them with rock, pop and alternative sounds.
For Generation Y, people make all the difference! The establishment of the right conditions and the provision of adequate opportunities for recognition and reward are No.1 priorities within an environment of mutual cooperation and self-development.
View event photo gallery here.


Sharon Natoli is Founding Director of Food & Nutrition Australia and an advisor to food makers, manufacturers, producers, research and development corporations and franchises. She has qualifications in nutrition and business marketing and for the past 25 years has worked with global and local food brands and producers, including a period working in-house with one of Australia's iconic food brands. She partners with her clients to assist them prepare for the future by sharing her insights around the health and nutrition related drivers shaping the future of food and advising on the application of these insights to innovation, marketing and business strategy.


So the music in Studio Ghibli films is kind of the best. Revisit these beautiful hour-long mixes if you're not convinced. The reason we bring it up is because this remix of the music from Spirited Away is a fascinating and entertaining interpretation, and it turns out that it's just the start of an entire album in this style, which is sort of like the jazzy, lo-fi hip-hop beat tapes that populate Bandcamp (via NPR).
The song is by Ghosting, who is really Melbourne producer Andrei Eremin, and he said the idea for the song just happened to pop in his head one day. When he realized how great the song turned out, he knew he had to create an entire album based on this idea.
"The mixtape started as a lightbulb moment to sample Spirited Away, one of my all-time favourite films," he wrote on Bandcamp. "I took out my keyboard on a whim, cut up the intro to the film and within 4 hours I'd finished the best track I'd ever made. It was a sign. From there the decision made itself - I had to sample every other Miyazaki film.
The mixtape is called Reimagining Miyazaki, and we won't have to wait that long to hear the rest of it, since it's set to be released on May 12. Are you going to give this project a listen, or are you going to give it a thousand million listens? Let us know what you think about the first song in the comments below.
Is Totoro secretly a demon from Hell?


Interested in industry, business, government or nonprofit careers? Want to learn more about PhD-level opportunities in these sectors? This career event is for PhDs and Postdocs from a variety of disciplines within H&S (Humanities included!), Engineering, Earth Sciences, Education and more.


text:
Heinrich Heine ist der Name folgender Person:

* Heinrich Heine (1797–1856), deutscher Dichter, Schriftsteller und Journalist
 Heinrich Heine (Maler) (1839–1916), deutscher Maler
 Heinrich Heine (Heimatforscher) (1860–1931) deutscher Lehrer und Heimatforscher
 Heinrich Otto Heine (1837–1906), deutscher Philologe und Gymnasialdirektor, siehe Otto Heine

Heinrich Heine ist der Name folgender Schiffe:
 Heinrich Heine (Schiff, 1938), Fracht- und Ausbildungsschiff der Deutschen Seereederei Rostock
 Heinrich Heine (Schiff, 1969), Ausflugsschiff der Köln-Düsseldorfer Deutsche Rheinschiffahrt AG
 Heinrich Heine (Schiff, 1975), Kühlschiff der Deutschen Seereederei Rostock
 Heinrich Heine (Schiff, 1991), Flusskreuzfahrtschiff der bulgarischen Reederei Giljam River Cruises

Heinrich Heine steht für:
 Heinrich Heine (Film), Fernseh-Filmbiografie von Klaus Emmrich und Herbert Knopp (1978)

redpajama_set_name: RedPajamaWikipedia


Your Lids for Children Cancer Treatments!
This is a cancer treatment fundraiser for children in Mexico. Our own Nancy Lindley is a sun-bird to this area of Mexico and a strong supporter of this valuable project.
All plastic lids (mayonnaise, margarine, water and soda bottles, milk jugs tops, etc.) are welcome and it would be great if the lids are rinsed. The box is in Community Hall.
Nancy reports that last year with this program alone 365 children were given free cancer treatments. This program works!
Thanks for your plastic lids for kids.


Canadian astronaut David Saint-Jacques is in Russia to prepare for his mission to the International Space Station in December.
When Canadian astronaut David Saint-Jacques blasts into orbit next week atop a Russian rocket, his family back on Earth will be getting help from Gov. Gen. Julie Payette.
Payette, a former astronaut who last travelled into orbit on the space shuttle Endeavour in 2009, plans to visit the Russian launch facility in Baikonur, Kazakhstan, for Saint-Jacques's liftoff on Dec. 3.
Canadian officials familiar with the visit say, in addition to representing the head of state, Payette will also have a formal role as Saint-Jacques's Casualty Assistance Calls Officer. The role typically involves liaising between the astronaut's family and different governments in the event of any problems on launch day.
Saint-Jacques, 48, is married with three children.
The Prime Minister's Office is expected to release more details about Payette's trip on Monday.
Payette was appointed governor general in July 2017, but her role helping the family pre-dates the appointment, according to one Canadian official.
Saint-Jacques's launch to the International Space Station — his first space voyage — is set for 6:30 a.m. ET on Dec. 3.
He will serve as the Soyuz co-pilot for the three-person mission alongside Russian mission commander Oleg Kononenko and American astronaut Anne McClain. He will also serve as the crew's doctor on board the ISS during a six-and-a-half-month stay.
Russia leases a Soviet-era facility in central Kazakhstan to launch its manned missions to the International Space Station.
Since the end of the U.S. Space Shuttle program, Russian spacecraft have been the only way to get to the ISS and dozens of astronauts of different nationalities, including Canadian Chris Hadfield, have made the trip.
Payette's attendance at the launch is unusual in several aspects.
Russia's takeover of Crimea in 2014 and its ongoing military involvement in separatist areas of eastern Ukraine have sent Canadian relations with Russia into a deep freeze.
Official contact between senior members of Canada's government and Russia have been practically non-existent in recent years.
Canada has sanctioned many senior members of Vladimir Putin's regime, including Dmitry Rogozin, the current head of Russia's Space Agency Roscosmos.
One of the Canadian officials told CBC News that no direct talks between Payette and any Russian representatives are planned in Baikonur, although there will be an official two-day visit to Kazakhstan following the launch.
Payette's status as a former astronaut and a member of a very small group of Canadians to fly in space is also significant. The hope is that her presence can help focus public attention on Canada's role in space, said the official.
Saint-Jacques will be the 10th Canadian to travel to space.
While Russia's vintage Soyuz program has proven reliable and safe for those flying to the ISS, the last mission on Oct. 11 ended in failure, forcing NASA astronaut Nick Hague and Russian cosmonaut Alexei Ovchinin to make an emergency landing. The pair were shaken but unharmed.
Saint-Jacques, Kononenko and McClain had originally been scheduled to blast off on Dec. 20, but the mission was moved up following the failed launch.
Investigators with NASA and Roscosmos have spent the last two months trying to solve the problem and ensure this launch is uneventful.


Get ready to expand your bookshelves at booth 641.
Home » Fresh Press » Get ready to expand your bookshelves at booth 641.
LitFire is bringing new reads that will inspire, delight, and thrill the bookworm in you. Treat yourself to with these amazing books.
On its second year at the ALA Midwinter Meetings & Exhibits, LitFire Publishing continues to celebrate the wonder of books with librarians, book lovers, and book trade professionals.
Discover great literary finds at booth 641, get giveaways, and meet our authors. See you at the Colorado Convention Center, from February 9 to 13, 2018!
Books like A Life Established by Faith and Patience by Shelly Kauffman, Acid and Bribery by Jeanne Ann Off, After the Third Day by J. J. Rodriguez, Little Worlds of Magic by Mary T. Kincaid, My Connie by Pradeep Berry, Outhouse to Whitehouse by Jimmy Mosley, Passion for the Piece by Cyndi Sibley, Presidential Disease by Robert Hrib, Squirrelly the Squirrel and Starlett by Larry Friend, Unraveling the Mahler Enigma by Franz Loschnigg, PhD, and many more will be displayed in at LitFire Publishing's booth.


Managing organizational cognition and learning has been the subject of many studies and publication and is considered a major source of competitive advantage in the knowledge-based economy in knowledge intensive and traditional business. Organizational Cognition and Learning: Building Systems for the Learning Organization addresses the concept of organizing that is centered around collective learning in organizations and on the learning organization paradigm. Organizational Cognition and Learning: Building Systems for the Learning Organization presents a theory of organizational learning based on a model of organizational memory, explaining organizational processes and dynamics through which organizational memory is built and updated. Organizational Cognition and Learning: Building Systems for the Learning Organization provides a methodology and several tools to elicit and map organizational memory contents, based on the analysis and modelization of discourses through qualitative and quantitative techniques, examples of applications, implications for practice, and a research agenda for the development of methodologies and systems for the learning organizations.


According to reports, Iran's Communication Minister expressed hope for the immediate start of the construction of an Iranian satellite in cooperation with Russia.
Iranian Communications Minister Mahmoud Vaezi said that Tehran hopes to sing an agreement on a free trade zone with the Eurasian Economic Union (EAEU) in the near future.
Iranian President Hassan Rouhani accepted invitation of Russian President Vladimir Putin to visit Moscow and the two countries' foreign ministries are to agree the date for the trip, according to Iranian Communications Minister Mahmoud Vaezi.
Iranian Minister of Communications said that Iran is planning to discuss new potential oil and gas contracts with Russian companies soon.
Iran sees opportunities to work with Russia's oil company LUKoil, including a possible cooperation agreement, Iranian Minister of Communication Mahmoud Vaezi said.
Iran's Supreme National Security Council Secretary Ali Shamkhani denied on Monday a link between the secret multimillion US payment to Iran and Tehran's nuclear program, in a comment to an Iranian news agency.
The recent $400 million payment from the United States to Iran was part of the agreement on the Islamic Republic's nuclear program, Iranian Minister of Communication Mahmoud Vaezi said.
Iranian Communications Minister Mahmoud Vaezi said that Tehran is in talks with the Roscosmos corporation on the implementation details of the nuclear project in Iran and is trying to agree on a suitable price.
Russian Energy Minister Alexander Novak said that he and Iranian Communications Minister, Mahmoud Vaezi discussed the issues related to the study into the possibility of establishing the Free Trade Area between countries and noted the progress made in this direction.
Russia and Iran have agreed to sign a roadmap for cooperation in the industrial field.
Co-chair of the Russia-Iran joint economic commission and Iranian Communications Minister Mahmoud Vaezi said that Tehran welcomes close cooperation with oil companies from Russia.
Iranian Minister of Communication Mahmoud Vaezi said that he discussed with his Russian counterpart Nikolai Nikiforov resumption of the Russian search engine Yandex work in Iran.
Iranian Minister of Communication Mahmoud Vaezi said that Iran had finished 92 percent of infrastructure works along the Qazvin-Rasht route, which will be completed by the end of this year.
Iran is expecting the visit of Russian Deputy Prime Minister Dmitry Rogozin to Tehran next week to discuss a wide range of technical cooperation issues, though S-300 deliveries could also be on agenda, Iranian Communications and Information Technology Minister Mahmoud Vaezi said Thursday.