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Can you derive the public key from a PGP encrypted message without knowing the message content?

aw flag

I am working on a system to transfer short messages while obfuscating the intended recipient.

In essence, it combines many messages encrypted using PGP, and periodically publishes a file containing those messages. The recipients would then download that file and try all messages against their secret key.

Given a message encrypted using PGP, could a potential attacker derive the public key from that message? And as such potentially gain information about the intended recipient?

This assumes that the public key is not published associated with personally identifiable information such as name or email address.

Though I know a multi node mixnet may be more effective and already have existing implementations, I am doing this as an exercise for myself.

Thank you for your time.

knaccc avatar
es flag
I'm not a PGP expert, but a quick look at RFC6637 https://datatracker.ietf.org/doc/html/rfc6637 says "20 octets representing a recipient encryption subkey or a master key fingerprint, identifying the key material that is needed for the decryption"
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