Signing

Acronym: IT

Signing a message, means authenticating that you have yourself assured the authenticity of the message (most of the time it means you are the author, but not necessarily). The message can be a text message, or someone else's certificate. To sign a message, you create its hash, and then encrypt the hash with your private key, you then add the encrypted hash and your signed certificate with the message. The recipient will recreate the message hash, decrypts the encrypted hash using your well known public key stored in your signed certificate, check that both hash are equals and finally check the certificate. The other advantage of signing your messages is that you transmit your public key and certificate automatically to all your recipients. There are usually 2 ways to sign, encapsulating the text message inside the signature (with delimiters), or encoding the message altogether with the signature. This later form is a very simple encryption form as any software can decrypt it if it can read the embedded public key. The advantage of the first form is that the message is human readable allowing any non-complaint client to pass the message as is for the user to read, while the second form does not even allow to read part of the message if it has been tampered with.