A plurality of message processors exchange public and secret information. Based on the exchanged information, each message processor computes a key sequence such that any one of a plurality of keys may be derived from the key sequence depending on key derivation data. A first message processor generates key derivation data that can be used to derive a particular key from among the plurality of keys. The first message processor sends a security token that includes the generated key derivation data to express to at least one other message processor how to derive the particular key from the computed key sequence. At least a second message processor receives the security token expressing how to derive the particular key from the computed key sequence. The first and/or second message processors apply the key derivation data to the computed key sequence to derive the particular key.