Jon Pretty

Is there a cryptographic protocol which allows two parties to check whether they know a common secret, without exchanging that secret?

@larsr_h can't they exchange hashes?

@posco I could come up with a protocol involving a trusted third party: A and B agree on a salt; both send their hashes to C; C decides eq.

@larsr_h @posco I could envision a simple two-party interactive one

@copumpkin @posco What does it look like?

@larsr_h @posco use DH to agree on common random key, then each party makes nonce, asks the other for a hmac(agreed_key, nonce, secret)

@copumpkin @larsr_h that has the same weakness as Lars mentioned: either party can brute force: both know the key, nonce.