O 2 TR: Offline Off-the-Record (OTR) Messaging

Abstract

Off-the-record (OTR) is a security protocol that can be used in privacy preserving instant messaging (IM) systems. However, the conventional OTR is not applicable in some practical scenarios (e.g., when communication network became disconnected) because OTR requires both parties to be online at the same time. To address this limitation, we extend the conventional OTR into a new protocol named offline OTR (O 2 TR). O 2 TR makes the conversation parties be able to handle an offline message even when a session connection is lost. To show the feasibility of the proposed protocol, we implemented a prototype to support O 2 TR based on the Gajim XMMP instant messaging platform. Our experiments showed that O 2 TR can reliably be used when a network party is broken down. Moreover, O 2 TR provides an efficient session refreshment which is about 34 % faster than the original OTR. © 2018, Springer International Publishing AG, part of Springer Nature.