Encryption/Hashing Algorithms AH and ESP are generic and do not specify the
exact mechanism used for encryption. This gives them the flexibility to work with a
variety of such algorithms and to negotiate which one to use as needed. Two common
ones used with IPsec are Message Digest 5 (MD5) and Secure Hash Algorithm 1
(SHA-1). These are also called hashing algorithms because they work by computing a
formula called a hash based on input data and a key.