> how would Signal inter-communicate with e2ee intact with say, Facebook Messenger? Couldn't you use Public Key Cryptography? Kind of like what we've done for

> how would Signal inter-communicate with e2ee intact with say, Facebook Messenger? Couldn't you use Public Key Cryptography? Kind of like what we've done for encryption between the Web Browser and Service Provider using PKI+TLS (HTTPS). Such-as...say each chat network having a certificate authority which crypto-signs each end-user's Public Key. With PKI used to encrypt messages between users. A 4096 PKI key can transmit 4KiB of data, which should be enough for most chat networks. For attachments or very large messages, can just copy how TLS uses PKI to transmit an AES key for decrypting a larger payload. The user's Private Key(s) can remain on phone/browser. To keep traffic e2e encrypted.