Session (software)
Session is a cross-platform end-to-end encrypted instant messaging application, focused on confidentiality and anonymity for the user. It is developed by The Oxen Project under the non-profit Oxen Privacy Tech Foundation. It uses a blockchain-based decentralized network for transmission. Users can send one-to-one and group messages, which can include files, voice notes, images and videos. Session offers applications for multiple platforms, including macOS, Windows, and Linux, in addition to mobile clients available on both iOS and Android. Features 
Session does not require a telephone number or email address to create an account. It uses a randomly generated 66-digit alpha-numeric number for user creation/identification. Communication (messages, voice clips, photos, and files) between users is end-to-end encrypted using the Session protocol. The Loki blockchain network is used by Session for transmissions. There was an independent review by the third party Quarkslab in 2021 that verified these claims. Development 
Session originally started as a fork of another messenger, Signal, with the idea of building upon its foundation. However, due to concerns about the centralized structure of Signal Protocol and the potential collection of unnecessary metadata, the team decided to deviate from it and instead created their own protocol, called Session Protocol. This approach allowed for increased anonymity and decentralization, but during the development process, the team encountered various challenges, leading to the necessity of abandoning or modifying many features. Limitations 
Session does not support two-factor authentication. Underlying protocols are still in a developmental phase. After migrating from Signal Protocol to own internally developed protocol, Perfect Forward Secrecy and deniable authentication was not implemented back. References

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Cross-platform software
Cryptographic software
Free and open-source Android software
Free instant messaging clients
Free security software
Free software programmed in Java (programming language)
Instant messaging clients programmed in Java
Internet privacy software
IOS software
Linux software
MacOS software
Windows software
Secure communication
Blockchain entities
Instant messaging clients