An integrated circuit restricts use of a data item and includes a data memory storing the data item; a value memory storing a value; a signature input that receives a signature derived from data in a data item field and a value in a value field, the signature being in a coded form; a decoding circuit that decodes the signature and outputs information representing the data in the data item field and the value in the value field; and a comparison circuit that receives the decoding circuit output, determines whether the information representing the data from the data item field corresponds to the stored data item and whether the information representing the value from the value field corresponds to the value stored in the value memory, and outputs a comparison signal according to the determinations. The circuit restricts the use of the data item according to the comparison signal.