QuickHash Library

API

HMAC API Overview

HMAC API assists you in generating Keyed-Hash Message Authentication Codes (HMACs).

HMACs can be generated in two modes: accumulative and non-accumulative.

The accumulative mode is applied when the data for which the HMAC is calculated (data) represents one or more continuous memory block(s) or when the data is created at runtime in many steps (for instance, when reading a file).

Non-accumulative mode can be applied when the data represents only one continuous memory block.

Note. When the data represents just one continuous memory block, both methods can be applied.

To generate the HMAC in the accumulative mode, perform the following:

• Allocate at least SLC_HMAC_CONTEXTSIZE( CONTEXTSIZE, BLOCKSIZE ) bytes for the context. CONTEXTSIZE and BLOCKSIZE from the previous notation are predefined constants for the context size and the block size for a specific hash algorithm. For example, you have to allocate at least SLC_HMAC_CONTEXTSIZE( SLC_MD5_CONTEXTSIZE, SLC_MD5_BLOCKSIZE ) bytes for the context if you need to calculate the HMAC using MD5 hash algorithm.

  All supported hash algorithms with their corresponding CONTEXTSIZEs and BLOCKSIZEs are listed in the table below.

  Algorithm Name	Algorithm CONTEXTSIZE	Algorithm BLOCKSIZE
  MD4	SLC_MD4_CONTEXTSIZE	SLC_MD4_BLOCKSIZE
  MD5	SLC_MD5_CONTEXTSIZE	SLC_MD5_BLOCKSIZE
  SHA-1	SLC_SHA1_CONTEXTSIZE	SLC_SHA1_BLOCKSIZE
  SHA-256	SLC_SHA256_CONTEXTSIZE	SLC_SHA256_BLOCKSIZE
  SHA-512	SLC_SHA512_CONTEXTSIZE	SLC_SHA512_BLOCKSIZE
  SHA-384	SLC_SHA384_CONTEXTSIZE	SLC_SHA384_BLOCKSIZE
  RIPEMD128	SLC_RIPEMD128_CONTEXTSIZE	SLC_RIPEMD128_BLOCKSIZE
  RIPEMD160	SLC_RIPEMD160_CONTEXTSIZE	SLC_RIPEMD160_BLOCKSIZE
  RIPEMD256	SLC_RIPEMD256_CONTEXTSIZE	SLC_RIPEMD256_BLOCKSIZE
  RIPEMD320	SLC_RIPEMD320_CONTEXTSIZE	SLC_RIPEMD320_BLOCKSIZE
  PANAMA	SLC_PANAMA_CONTEXTSIZE	SLC_PANAMA_BLOCKSIZE
  TIGER	SLC_TIGER_CONTEXTSIZE	SLC_TIGER_BLOCKSIZE

• Call the SL_HMAC_Init function to initialize the context with a key.

Note. You can use SL_HMAC_InitKeyStr function (instead of SL_HMAC_Init function) if the key represents a null-terminated string.

• Call the SL_HMAC_Update function for each continuous memory block of data to perform the calculations.

Note. You can use SL_HMAC_UpdateStr function (instead of SL_HMAC_Update function) if the data represents a null-terminated string.

• Call the SL_HMAC_Final or the SL_HMAC_FinalHex function to obtain the HMAC.

Note. Call the SL_HMAC_FinalHex function when you need to retrieve the hexadecimal string representation of the HMAC.

To generate the HMAC in the non-accumulative mode, perform the following:

• Call the SL_HMAC_Calculate or the SL_HMAC_CalculateHex function to calculate and retrieve the HMAC.

Note 1. Call the SL_HMAC_CalculateHex function when you need to retrieve the hexadecimal string representation of the HMAC.

Note 2. You can use SL_HMAC_CalculateStr and SL_HMAC_CalculateStrHex functions (instead of SL_HMAC_Calculate and SL_HMAC_CalculateHex functions) if the data represents a null-terminated string.

HMAC API Functions   |   Useful Links   |   HashCalc