In accordance with a method for communicating a control word (CW) from a client such as an encryptor to a server such as the entitlement control message generator (ECMG) of a conditional access system (CAS), communication is established between the client and server over a secure connection. A control word to be encrypted is received by the client and encrypted using a first and second key. The first key is a global secret key (GSK) that is known to the client and the server without being communicated over the secure connection. The second key is a control word encryption key (CWEK) that is derived from a locally generated client nonce (CN) and a server nonce (SN) obtained from the server over the secure connection. The encrypted control word (ECW) is sent to the server over the secure connection.