IPsec (Internet Protocol Security)
A set of protocols developed by the IETF to support secure exchange of packets at the IP layer.
IPsec Algorithms And Keys
Currently IPsec is mainly described by the three followings RFCs:
* RFC4301, Security Architecture for the Internet Protocol, S. Kent, K. Seo, December 2005, PROPOSED STANDARD.
* RFC4302, IP Authentication Header, S. Kent, December 2005, PROPOSED STANDARD.
* RFC4303, IP Encapsulating Security Payload (ESP), S. Kent, December 2005, PROPOSED STANDARD.
The Algorithms to use and their requirements are described in RFC4305: Cryptographic Algorithm Implementation Requirements for Encapsulating Security Payload (ESP) and Authentication Header (AH), D. Eastlake 3rd, December 2005, PROPOSED STANDARD.
You also may use some others Cryptographic Algorithm (have a look at the IANA for some other examples).