This part of ISO/IEC 11770 specifies key establishment mechanisms for multiple entities to provide procedures for handling cryptographic keying material used in symmetric or asymmetric cryptographic algorithms according to the security policy in force.It defines symmetric key based key establishment mechanisms for multiple entities with a key distribution centre (KDC), and defines the symmetric key establishment mechanisms based on general tree based structure with both individual rekeying and batched rekeying. It also defines key establishment mechanisms based on key chain with both unlimited forward key chain and limited forward key chain. Both key establ