A security system for controlling access to encrypted information, comprising: a memory for storing at least one decryption key for use in decrypting an encrypted item of information, the decryption key being associated with a security code which can be used to determine whether the security system is authorized to send encrypted copies of the decryption key to others. If the security system is authorized to send an encrypted copy of the decryption key, it encrypts the decryption key and propagates the encrypted copy of the decryption key. Each time the security system propagates a decryption key, it includes as part of the decryption key an identifier indicating the identity of a sender's key. A user can append a control word against their identity in the decryption key to instruct the security system to initiate a message to them or an agent informing them of the propagation of the key and giving information concerning that propagation.