Secure self learning system

DETAILED DESCRIPTION The invention provides, in the first instance, a method of operating an encoder which includes the steps of: storing a serial number; storing at least one of the following: a seed; and a key which is generated using a manufacturer's master key and at least one of the following: the seed; and the serial number; and transferring key generation information selected at least from: the seed; the serial number; and information derived from applying the key and an algorithm to an input value.
The input value may include information selected at least from: a management code; a counter value; and information relating to a command.
In one embodiment the method includes the steps of: storing a plurality of parameter sets, each parameter set including information selected at least from: a respective serial number; a respective seed; a respective key; and respective information derived from applying the said respective key and the algorithm to a respective input value; selecting a parameter set; and transferring the respective key generation information for the selected parameter set.
Each input value may include information selected at least from: a respective management code; a respective counter value; and information relating to a command.
The invention also extends to a method of operating a decoder which includes the steps of: storing a manufacturer's masterkey; receiving a signal which contains key generation information selected at least from: a seed; a serial number; and encoded information derived from applying a first key and an algorithm to an input value; and generating a second key using at least the key generation information and the manufacturer's master key.
The method may include the steps of storing at least one of: the second key; the key generation information; and the serial number.
In one embodiment the received signal includes the encoded information and the method includes the steps of: decoding the encoded information using a decoding algorithm and a previously generated second key to obtain a decoded input value which includes information selected at least from: a management code; a counter value; and information relating to a command; and storing the decoded input value