A messaging system is needed with the following properties:

- sneakernet/airgapped cryptography

- immutable preservation of public discourse

- support/preference for anonymity

- integration with or expansion of one or more systems that are already in-use, with one or more existing development and user communities

- peer to peer, disaster-ready

- cryptographic delivery (and/or read) receipts

- simple, clear reimplementable and third-party-maintainable design, making heavy reuse of few basic parts

Although some of the above properties are common, some are very rare.  The rare properties should be prioritised.