ICSF is a software element of z/OS. ICSF works with the hardware cryptographic features and the Security Server (RACF element) to provide secure, high-speed cryptographic services in the z/OS environment. ICSF provides the application programming interfaces by which applications request the cryptographic services. ICSF is also the means by which the secure cryptographic features are loaded with master key values, allowing the hardware features to be used by applications. The cryptographic feature is secure, high-speed hardware that performs the actual cryptographic functions. Your processor hardware determines the cryptographic feature available to your applications.