5. Instantiation
This document specifies HMAC using a generic cryptographic hash function (denoted by H). Specific instantiations of HMAC need to define a particular hash function. Current candidates for such hash functions include:
- SHA-1 [SHA] - outputs L=20 bytes (160 bits)
- MD5 [MD5] - outputs L=16 bytes (128 bits)
- RIPEMD-128/160 [RIPEMD] - outputs L=16 or 20 bytes
These different realizations of HMAC will be denoted by:
- HMAC-SHA1
- HMAC-MD5
- HMAC-RIPEMD
All these hash functions use a block length of B=64 bytes.
For specific instantiations, implementers should refer to the definitions and specifications of the respective hash functions, ensuring that the parameters B (block length) and L (output length) are correctly applied as defined in section 2.