(n+1)sec – a protocol for distributed multiparty chat encryption
Some of you might recognize NCC Group, the company that performed the cryptographic review. They acquired Matasano, tptacek&#x27;s prior company. Collectively they have some of the most talented pentesters and cryptographic analysts.<p>It&#x27;s a safe bet that the (n+1)sec protocol has an excellent security rating on the basis that they only found one low-severity issue and two informational issues during the analysis.<p><a href="https:&#x2F;&#x2F;github.com&#x2F;equalitie&#x2F;np1sec&#x2F;raw&#x2F;master&#x2F;doc&#x2F;NCC_Group_Equalitie_N1Sec_Report_2017-07-21_v1.pdf" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;equalitie&#x2F;np1sec&#x2F;raw&#x2F;master&#x2F;doc&#x2F;NCC_Group...</a><p>Note the caveat:<p><i>NCC Group reviewed the full specification, however, only the portions of the library that lined up with the protocol were reviewed. NCC Group did not perform a line-by-line review of the entire library. Additionally, the review focused on the library and not a chat client implementing the library.</i><p>This means that the theory is sound, but the library itself wasn&#x27;t actually pentested. That isn&#x27;t an indication that there are problems -- just that no one has looked for them yet. As a specific example: <a href="https:&#x2F;&#x2F;github.com&#x2F;equalitie&#x2F;np1sec&#x2F;blob&#x2F;05b73b506b83be9724c61bdd46973eee96fa2e31&#x2F;src&#x2F;message.cc#L159-L162" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;equalitie&#x2F;np1sec&#x2F;blob&#x2F;05b73b506b83be9724c...</a> It sounds like assessing memory errors was outside the scope of the security review, so it seems unlikely that anyone was thinking about questions like &quot;is there a way for an attacker to trick buffer.size() into becoming -1 and DoSing the system?&quot; It was focused mostly on the mathematical soundness of the cryptosystem.<p>It&#x27;s extraordinarily expensive to schedule a two-week pentest, but implementation errors are far more commonly exploited than attacking the properties of a cryptosystem directly. It might be good to schedule an additional pentest if possible.<p>That said, this is mostly incidental. Congrats on shipping!