Introduction to OTR

Lecture by Alexander Færøy at PROSA Cryptoparty in Copenhagen, Denmark on January 25, 2015.

In this lecture, we went over the Off The Record (OTR) messaging protocol for secure communication. The target group for this presentation was people who were already aware of the existence of OTR but were interested in understanding it better.

We went over the different concepts that are important to understand in OTR: encryption, authentication, deniability, and perfect forward secrecy. We showed how OTR is agnostic when it comes to transport protocols, and how it is used together with Jabber (XMPP), Internet Relay Chat, and Facebook messenger. Additionally, we went over how the Socialist Millionaires Protocol can be used in OTR to authenticate a remote contact.