A method of providing a secure communication between first and second
devices is described. The method includes encrypting a random key using
an encryption key at a first device and transferring the encrypted random
key to the second device for encryption of data communicated from the
second device to the first device. The encrypted data received from the
second device is decrypted using the random key. The method typically
includes transferring a control word encrypted with an encryption key to
the second device for decryption, and encryption using the random key.
The encrypted control word received from the second device is then
decrypted using the random key. The invention extends to a method of
enabling a decoder, and to a decoder, to decode a data stream. It also
extends, inter alia, to a method of authenticating an enabling device and
to an enabling device.