What Exactly Is End-To-End Encryption?
medium.com
medium.com
Companies that offer encryption products use various mechanisms to allow the sender and the recipient to end up with matching keys. It is surprisingly difficult to do correctly.
It is not enough that the communication stays encrypted from the sender, through the server, and to the recipient. It is also important that no one besides the sender and recipient has the ability to decrypt that communication.
Haven't tried the software or given their paper a proper read yet.
Initial thoughts: No forward/future secrecy. Stores user private keys on their server encrypted with user supplied passwords. Their centralized service is trusted for identity. Not sure how users update their secrets if compromised.
Adding proper E2E crypto to legacy email is hard. I don't think they solve it.