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Revery: v0 of a secure messaging protocol (github.com)

submitted 1 day ago by slugr@leminal.space to c/privacy@lemmy.ml

8 comments fedilink hide all child comments

i started a (very niche) private messaging protocol & little CLI app demo. i’m no security expert, so any feedback or questions would be appreciated.

the gist is an ephemeral message exchange without identities. the goal is ultimate deniability.

the interesting (and weird) part is that messages are encrypted but not authenticated. this means an imposter could show up if they know the shared secret. otoh this means you can deny anything you say.

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[–] slugr@leminal.space 2 points 21 hours ago (3 children)

interesting point! i chose symmetric shared key because it means you can’t prove who sent what message.

the shared secret does add some authentication, which i think is necessary. the goal is it only creates enough to be practical (a random person can’t eavesdrop), but not enough to prove things. messages themselves still aren’t authenticated by any one person.

[–] JumpyWombat@lemmy.ml 2 points 20 hours ago (2 children)

A shared secret implies that the message was sent by someone who knows the shared secret, and that restrict the number of potential senders.

If you mail a message with gpg, everyone knows the public key, and the message is still safe.

[–] slugr@leminal.space 1 points 20 hours ago (1 children)

you’re not wrong, but that’s just the trade off that has to be made, i think. it’s the only way i can think to do it, at least. need -some- authentication for practical usability.

your gpg example removes the deniability since it proves who wrote the message.

[–] JumpyWombat@lemmy.ml 1 points 20 hours ago

your gpg example removes the deniability since it proves who wrote the message.

You confuse digitally signing a message with the sender's private key, and encrypting a message with the recipient's public key.