Messaging LayerSecurity (MLS) is a security layer in the Messenger layer model for end-to-end encryption (E2EE). The MLS protocol is being developed by an IETF working group as an efficient and secure group messaging protocol and is intended to make large group messaging
secure. The IETF has specified several criteria for the MLS protocol. These include the confidentiality of the messages transmitted, which can only be read by authorized group members. In addition, the integrity and authenticity of the messages, which ensures that they can only be sent by authenticated users and cannot be changed during transmission, and as a further criterion, the transparency of
the group members is required. According to this, each member of a group should be able to verify the authenticity of each individual group member. In terms oflayer architecture, Messaging Layer Security (MLS) lies between
theapplication layer with its various message formats and Transport Layer Security (TLS). The MLS protocol interfaces
with the authentication service. As far as encryption is concerned, crypto keys can be generated asynchronously without requiring two participants to join the session at the same time. In addition, forward secrecy (FS) ensures that no data can be reconstructed after a session. The second security mechanism, Post-Compromise Security, prevents a compromising node from compromising data that has already been transmitted.