The Signal protocol is only responsible for encrypting and decrypting messages. Yeah, Keychat uses Signal protocol to encrypt / decrypt message.
Interesting, I just read about the double ratchet algorithm: https://signal.org/docs/specifications/doubleratchet/#double-ratchet Does this mean that users could publish their nsec and their old DMs would not be accessible?
Yeah, check this post nostr:note1ffgsgvkltl96wzwe6lakv2ntjfkq2u48msx57mrvnnhtyde5s2js8antlr