In computing, Internet Key Exchange (IKE or IK***) is the protocol used to set up a security association (SA) in the IPsec protocol suite. IKE builds upon the Oakley protocol and ISAKMP. IKE uses X.509 certificates for authentication - either pre-shared or distributed using DNS (preferably with DNSSEC) and a Diffie–Hellman key exchange - to set up a shared session secret from which cryptographic keys are derived. In addition, a security policy for every peer which will connect must be manually maintained.