A technique for generating a cryptographic key is provided. The technique is particularly useful for protecting the communication between two entities cooperatively running a distributed security operation. The technique comprises providing at least two parameters, the first parameter comprising or deriving from some cryptographic keys which have been computed by the first entity by running the security operation; and the second parameter comprising or deriving from a token, where the token comprises an exclusive OR of a sequence number (SQN) and an Anonymity Key (AK). A key derivation function is applied to the provided parameters to generate the desired cryptographic key.