http://ssd.iykpqm7jiradoeezzkhj7c4b33g4hbgfwelht2evxxeicbpjy44c7ead.onion/ps/module/how-use-otr-macos
A " key fingerprint " is a string of characters like "342e 2309 bd20 0912 ff10 6c63 2192 1928,” that’s used to verify a longer public key. Exchange your fingerprints through another communications channel, such as Twitter DM or email, to make sure that no one is interfering with your conversation.