It's a reasonable idea that already has use in displaying cryptographic fingerprints. Typically when servers present a certificate, if the cert is untrusted, a

It's a reasonable idea that already has use in displaying cryptographic fingerprints. Typically when servers present a certificate, if the cert is untrusted, a fingerprint (a hash of the public key) is shown to the user. This is meant to caution the user: if all of a sudden they see a fingerprint that they don't recognize, it might be somebody malicious trying to capture your traffic! Instead of presenting the fingerprint as a big hexadecimal string, some clients instead produce ASCII art and display that instead, on the theory that the human brain is better at memorizing that than a big string of digits. For example, OpenSSH: http://it.toolbox.com/blogs/unix-sysadmin/visual-ssh-fingerprints-with-new-openssh-51-release-26175 http://it.toolbox.com/blogs/unix-sysadmin/visual-ssh-fingerp... I would argue this has even more use in a system that is trying to warn about changes, rather than about possible malicious attackers. After all, in the SSH example above, an attacker just needs to get a certificate that looks close enough to the real one that the user will accept it.