ANSI ISO IEC-9797-2-2002 pdf download Information technology — Security techniques — Message Authentication Codes (MACs) — Part 2: Mechanisms using a dedicated hash-function
1 Scope
This part of ISO/IEC 9797 species three MAC algo- rithms that use a secret key and a hash-function (or its round-function) with an n-bit result to calculate an m-bit MAC. These mechanisms can be used as data integrity mechanisms to verify that data has not been altered in an unauthorised manner. They can also be used as message authentication mechanisms to provide assurance that a message has been originated by an en- tity in possession of the secret key. The strength of the data integrity mechanism and message authentication mechanism is dependent on the length (in bits) k and secrecy of the key, on the length (in bits) n of a hash- code produced by the hash-function, on the strength of the hash-function, on the length (in bits) m of the MAC, and on the specic mechanism.
The three mechanisms specied in this part of ISO/IEC 9797 are based on the dedicated hash- functions specied in ISO/IEC 10118-3. The rst mech- anism specied in this part of ISO/IEC 9797 is com- monly known as MDx-MAC. It calls the complete hash- function once, but it makes a small modication to the round-function by adding a key to the additive constants in the roundfunction. The second mechanism specied in this part of ISO/IEC 9797 is commonly known as HMAC. It calls the complete hash-function twice. The third mechanism specied in this part of ISO/IEC 9797 is a variant of MDx-MAC that takes as input only short strings (at most 256 bits). It oers a higher performance for applications that work with short input strings only. This part of ISO/IEC 9797 can be applied to the se- curity services of any security architecture, process, or application.
2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provi- sions of this part of ISO/IEC 9797. For dated refer

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