RSA Security 5 manual Output considerations

AI_HMAC

Output considerations:

The output of B_DigestFinal will be the length of the output of the digest specified; for instance, 20 bytes when digestInfoType is AI_SHA1.

9 2 R S A B S A F E C r y p t o - C L i b r a r y R e f e r e n c e M a n u a l