Essential Guide to Computing: The Story of Information Technology, The

Digital Signatures

Public key encryption not only helps to secure messages, it can also verify the identity of the sender using a technique known as a digital signature (DS). The DS takes advantage of the fact that the public key/private key thing works both ways. Something encrypted with the private key can be decrypted with the public key, as well as the reverse. This means that if you got a public key from Joe Smith, and you got a message from him that he had coded with his private key, you could use the public key to read it. And you would know that it came from Joe, since the public key wouldn't work on anything but the private key with which it is paired. Thus, anything encoded with a private key is, in effect, a digital signature.

Tech ...