3. Introduction:
The IP authentication scheme uses a called
Hash Message Authentication Codes (HMAC).
If H-mac is an encrypted message in RFC
1024.
HMAC uses a shared key between two parties
rather than public key methods for message
authentication.
4. Objectives for HMAC:
To use, without modifications, available hash
function.
To allow for easy replaceability.
To hash function in case faster , more secure
the hash function.
To use and handle keys in a simple way.
5. HMAC security:
1. The security of HMAC relates to that of the
underlying hash algorithm.
2. Attacking HMAC :
Brute-force attack on key used.
Birthday attack is an observe a
very large number of message. Choose hash
function used based on speed versus security
constraints.
Note that HMAC is more secure than MD5 for
birthday attack.