A method for supporting handling of change of serving Access and Mobility Management Function for a user equipment , wherein said method is performed at a target Access and Mobility Management Function and comprises: - sending (S1) of, from the target Access and Mobility Management Function , a security context request to a source Access and Mobility Management Function ; - receiving of, in said target Access and Mobility Management Function , a security context in reply from the source Access and Mobility Management Function , wherein said security context comprises a parameter which identifies a Security Anchor Function Access and Mobility Managing Function , said Security Anchor Function Access and Mobility Management Function being an Access and Mobility Management Function that keeps a key denoted Kseaf and serves as a root key for derivation of core network and access network keys and is shared with said user equipment and has resulted from a primary authentication procedure for network access between the user equipment and an authentication server function via the Security Anchor Function Access and Mobility Management Function ; - identifying the Security Anchor Function Access and Mobility Managing Function using the parameter, and - deciding (S4) an authentication strategy based on a security policy depending on the location of said source Access and Mobility Management Function and said identified Security Anchor Function Access and Mobility Management Function , wherein the authentication strategy comprises one of: an execution of a new authentication procedure, and a request from the target Access and Mobility Management Function of a new core network key derived from the Kseaf to said Security Anchor Function Access and Mobility Management Function . - sending (S1) of, from the target Access and Mobility Management Function , a security context request to a source Access and Mobility Management Function ; - receiving of, in said target Access and Mobility Management Function , a security context in reply from the source Access and Mobility Management Function , wherein said security context comprises a parameter which identifies a Security Anchor Function Access and Mobility Managing Function , said Security Anchor Function Access and Mobility Management Function being an Access and Mobility Management Function that keeps a key denoted Kseaf and serves as a root key for derivation of core network and access network keys and is shared with said user equipment and has resulted from a primary authentication procedure for network access between the user equipment and an authentication server function via the Security Anchor Function Access and Mobility Management Function ; - identifying the Security Anchor Function Access and Mobility Managing Function using the parameter, and - identifying the Security Anchor Function Access and Mobility Managing Function using the parameter, and - deciding (S4) an authentication strategy based on a security policy depending on the location of said source Access and Mobility Management Function and said identified Security Anchor Function Access and Mobility Management Function , wherein the authentication strategy comprises one of: an execution of a new authentication procedure, and a request from the target Access and Mobility Management Function of a new core network key derived from the Kseaf to said Security Anchor Function Access and Mobility Management Function . an execution of a new authentication procedure, and a request from the target Access and Mobility Management Function of a new core network key derived from the Kseaf to said Security Anchor Function Access and Mobility Management Function . <EOS>