Off-the-record (OTR) messaging is a secure message transmissionbetween two communication partners in instant messaging. In the OTR process, the message content is encrypted using end-to-end encry ption( E2EE) so that no third party can read the message content.
OTR messaging uses authentication to ensure that the communication partner is the intended partner. During communication, in which both communication partners must be online at the same time, it is ensured that the conversation partner has not changed and that the message content is authentic and unchanged. Since the procedure works without a digital signature, it is no longer possible to trace which communication partner made which statement after a session has ended.
Another communication protocol with end-to-end encryption is the signal protocol. The difference between the OTR and the signal protocol is that with the signal protocol, both communication partners do not have to be online at the same time.