Encapsulating Security Payload

aliases:

• ESP

A core protocol of IPsec.

ESP is used to encrypt only the payload, and doesn't compute an ICV exactly like AH does. Instead, ESP attaches three fields to the packet:

• a header
• a trailer
• an ICV computed without the IP header

With ESP, algorithms for both confidentiality (symmetric cipher) and authentication/integrity (hash function) are usually applied together. It is possible to use one or the other, however.