Authentication Using Digital Signatures

Authentication can be accomplished in a number of ways. These include:

• Fixed passwords.

• Time-variant passwords.

• Digital signatures.

Digital signatures are by far the most popular and most reliable method of authentication. Digital signatures usually combine a hash with another cryptographic operation (typically asymmetric encryption) to produce a type of check that not only verifies that the data was not altered in transit, but also assures that the named sender is, in fact, the actual sender of the data.

For example, if we provide a digital signature based on SHA1 with RSA encryption, this means that an SHA1 hash of the message was encrypted with the private key of the sender. Because the SHA1 hash is very collision resistant, and assuming the private key of the sender is known only by the sender, then verifying such a signature indicates that the message was not altered and that it was sent by the named sender.