Extension to XMPP for multi-client end-to-end encryption
Logo of OMEMO
OMEMO is an extension to the Extensible Messaging and Presence Protocol (XMPP) for multi-clientend-to-end encryption developed byAndreas Straub. According to Straub, OMEMO uses theDouble Ratchet Algorithm "to provide multi-end to multi-end encryption, allowing messages to be synchronized securely across multiple clients, even if some of them are offline".[1] The name "OMEMO" is arecursive acronym for "OMEMO Multi-End Message and Object Encryption".It is an open standard based on the Double Ratchet Algorithm and thePersonal Eventing Protocol (PEP, XEP-0163).[2]OMEMO offers future andforward secrecy and deniability with message synchronization and offline delivery.
In comparison withOTR, the OMEMO protocol offers many-to-many encrypted chat, offline messages queuing, forward secrecy, file transfer, verifiability and deniability at the cost of slightly larger message size overhead.[3]
The protocol was developed and first implemented by Andreas Straub as aGoogle Summer of Code project in 2015. The project's goal was to implement a double-ratchet-based multi-end to multi-end encryption scheme into an Android XMPP-based instant messaging client calledConversations.It was introduced in Conversations and submitted to theXMPP Standards Foundation (XSF) as a proposedXMPP Extension Protocol (XEP) in the autumn of 2015 and got accepted asXEP-0384 in December 2016.[1]
In July 2016, theChatSecure project announced that they would implement OMEMO in the next releases. ChatSecure v4.0 supports OMEMO and was released on January 17, 2017.[4][5]
A first experimental release of an OMEMO plugin for the cross-platform XMPP clientGajim was made available on December 26, 2015.[6]
In June 2016, the non-profit computer security consultancy firm Radically Open Security published an analysis of the OMEMO protocol.[7]
^Radically Open Security (June 1, 2016)."OMEMO: Cryptographic Analysis Report"(PDF). Amsterdam: Radically Open Security.Archived(PDF) from the original on April 4, 2025. RetrievedApril 10, 2025.
