Patent ID: 7698718

Claim:
A semiconductor integrated circuit for restricting use of a data item stored within the circuit, the circuit comprising: a data memory for storing the data item; one or more value memories, each value memory arranged to store a value; a signature input for receiving a signature, the signature being derived from data in a data item field and a value in a first value field, the signature being in a coded form generated according to an algorithm; a decoding circuit arranged to decode the signature and to extract and output information representative of the data in the data item field and information representative of the value in the value field; and a comparison circuit arranged to receive the output of the decoding circuit and to determine whether the information representative of the data extracted from the data item field of the signature corresponds to the data item stored in the data memory and whether the information representative of the value extracted from the value field of the signature corresponds to a corresponding value stored in one of the one or more value memories, and further arranged to output a comparison signal according to results of the determinations; in which the circuit is arranged to restrict the use of the data item stored within the circuit according to a state of the comparison signal.