My clients have to exchange public keys. To ensure security they are exchanging fingerprints and typing them into the computer by hands.

I want the fingerprints to be as short as possible.

I am using libsodium for encryption, which uses Curve25519. What is the shortest fingerprint I can generate which would still ensure security?

  • 2
    $\begingroup$ Note that it might be possible to use a short-authentication-string (SAS) instead of a fingerprint. Since those are not vulnerable to offline attacks, they can be much shorter. $\endgroup$ – CodesInChaos Dec 18 '15 at 15:00
  • $\begingroup$ @CodesInChaos: Oh, I did not know that possibility. That is great! $\endgroup$ – Nathan Dec 18 '15 at 15:27

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