Keychat is an app. It supports protocols and is open source but which other apps are compatible?
To my understanding, WN explored signal and MLS, too and decided to go with more advanced tools to be ...
Keychat’s one-to-one messages and small-group messages are encrypted using the Signal protocol, while large-group messages are encrypted using the MLS protocol. Marmot (WhiteNoise), on the other hand, encrypts all messages—both one-to-one and group messages—using MLS.
It’s worth emphasizing that for one-to-one messaging, the Signal protocol is more efficient (and therefore more secure), because the new public key needed to advance the DH ratchet (which provides post-compromise security) is carried in the header of normal messages, without requiring extra messages to transmit a new public key. In Keychat, as long as the two parties exchange messages back and forth, the DH ratchet advances automatically.
By contrast, if MLS is used to encrypt one-to-one chats, advancing the ratchet responsible for post-compromise security is less efficient and requires separate messages to transmit new keys. This is largely because MLS was designed with large-group messaging as its primary use case.
MLS is built for large groups; one-to-one support is a byproduct rather than an optimization target.
It’s worth emphasizing that for one-to-one messaging, the Signal protocol is more efficient (and therefore more secure), because the new public key needed to advance the DH ratchet (which provides post-compromise security) is carried in the header of normal messages, without requiring extra messages to transmit a new public key. In Keychat, as long as the two parties exchange messages back and forth, the DH ratchet advances automatically.
By contrast, if MLS is used to encrypt one-to-one chats, advancing the ratchet responsible for post-compromise security is less efficient and requires separate messages to transmit new keys. This is largely because MLS was designed with large-group messaging as its primary use case.
MLS is built for large groups; one-to-one support is a byproduct rather than an optimization target.
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