Keep in mind that any time a message is on flash storage there might be a hidden copy kept for flash technical reasons. It is hard to get to (particularly if th

Keep in mind that any time a message is on flash storage there might be a hidden copy kept for flash technical reasons. It is hard to get to (particularly if the disk is encrypted) but might still be accessible in some cases. I think encrypted messengers should have a "completely off the record" mode that can easily be switched on and off. Such a mode would guarantee that your messages are never stored anywhere that might become permanent. When you switch it off then everything is wiped from memory. That might be a good time to ensure any keys associated with a forward secrecy scheme are wiped as well.