AH&ESP in IPSec

Uses of Authentication Header (AH)

• Provide Authentication Services
• Verifies the originator of a message
• Verifies that data has not been changed on routing

Uses of Encapsulating Security Payload (ESP)

• Encrypted the IP datagram
•  AH ensures integrity but not privacy

    Example of AH&ESP

   #ah-md5-hmac AH-HMAC-MD5 transform  

   #ah-sha-hmac AH-HMAC-SHA transform  

   #esp-3des ESP transform using 3DES(EDE)cipher (168 bits) 

   #esp-des ESP transform using DES cipher (56 bits) 

   #esp-md5-hmac ESP transform using HMAC-MD5 auth 

   #esp-null ESP transform w/o cipher 

   #esp-sha-hmac ESP transform using HMAC-SHA auth 

   Command in CISCO Router

   Config(config)# crypto ipsec transform-set CorpHQ-vpn esp-3des esp-md5-hmac

   Config(config)# mode (tunnel or transport)