As we march along to a release, I have added better error handling in the mac and iOS client. A lot of this is focused on OMEMO. The most recent update today includes these changes in addition to fixes to sending/receiving aesgcm images. In the new error messages I have tried my best to provide some debugging info or some action that could be taken to potentially resolve this issue. It also lets me know in user feedback where an error in Monal my be.
If someone sends a 16 byte iv message this is what you will see:
Encrypted message was sent in an older format Monal can’t decrypt. Please ask them to update their client. (GCM error)
If the key was decrypted but an error was returned by lib signal:
There was an error decrypting this encrypted message (Signal error). To resolve this, try sending an encrypted message to this person.
If the message was not encrypted for this device it would be nice ot know what this device meant for the other party to verify:
Message was not encrypted for this device. Please make sure the sender trusts deviceid 123456 and that they have you as a contact.