Secure XML: The New Syntax for Signatures and Encryption

2.6. Digital Signatures

You can use public key authentication to produce “digital signatures.” These signatures have a very desirable characteristic—namely, it is computationally infeasible for anyone without the private key to produce a signature that will verify for a given message. Modern digital signatures consist of (1) a message and (2) a message digest of that message asymmetrically transformed under a private key of the signer. See Figure 2-5.

Figure 2-5. Digital signatures

Because message digests are short, fixed-length quantities, the slowness of public key algorithms has minimal effects on processing. The critical need to be sure you ...