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  SQL Server Tips by Gama and Naughter

Hash Message Authentication Code

A Hash Message Authentication Code (HMAC) is a one-way function, which is also dependent on a shared secret key. It can be used to determine whether a message sent over an insecure channel has been tampered with. The sender computes the HMAC for the data to send and sends both the data and HMAC to the receiver. The receiver then regenerates the HMAC and compares it to the received HMAC. Any change to the received data or HMAC will cause the calculated and received HMAC values to differ. XPCrypt includes support for MD2, MD4, MD5 and SHA1 HMACís.

Each HMAC implemented in this chapter uses the syntax ďXP_AlgorithmName_HMACí

The above book excerpt is from:

Super SQL Server Systems
Turbocharge Database Performance with C++ External Procedures

ISBN: 0-9761573-2-2
Joseph Gama, P. J. Naughter  


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