OTR [1], Axolotl [2] and OMEMO [3] all provide Perfect Forward Secrecy, which in turn means that you can&#x27;t (or should not be able to) read your archived messages. And with OTR can&#x27;t send messages to offline contacts. OpenPGP does not provide this property, which allows you to read your encrypted messages in the archive as long as you have access to your OpenPGP secret key and it allows you to send messages to offline contacts.<p>1: <a href="https:&#x2F;&#x2F;otr.cypherpunks.ca&#x2F;" rel="nofollow">https:&#x2F;&#x2F;otr.cypherpunks.ca&#x2F;</a>
2: <a href="https:&#x2F;&#x2F;github.com&#x2F;WhisperSystems&#x2F;Signal-Android&#x2F;wiki&#x2F;ProtocolV2" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;WhisperSystems&#x2F;Signal-Android&#x2F;wiki&#x2F;Protoc...</a>
3: <a href="http:&#x2F;&#x2F;conversations.im&#x2F;omemo&#x2F;" rel="nofollow">http:&#x2F;&#x2F;conversations.im&#x2F;omemo&#x2F;</a>