Introduction to Network Security, 2nd Edition

Chapter 4Data Authentication

Data authentication has two purposes: certify the origin of the data and convince the user that the data has not been modified or fabricated. Data authentication is a critical mechanism to maintain data integrity and nonrepudiation. Data authentication may be achieved either using conventional encryption algorithms or using public-key cryptography.

Suppose that Alice and Bob share a common secret key . Alice wants to send a data string to Bob and convince Bob that does indeed come from her without being modified during transmission. This can be done as follows: Alice sends together with to Bob, where and is a conventional encryption algorithm agreed on by Alice and Bob. Because only Alice and Bob know , Bob can use to decrypt to get . Bob will be convinced ...