Patent ID: 7251734

Claim:
A secure integrated circuit including storage means in which confidential data is stored, such as an encryption programme and at least an encryption key, a microprocessor unit for executing the encryption programme, an oscillator stage supplying clock signals for clocking the sequence of operations in the microprocessor unit, and a random number generator connected to the microprocessor unit, the oscillator stage being arranged to receive at least a random number generated by the random number generator so as to configure said oscillator stage so that it generates clock signals, whose frequency depends on the random number received, wherein the oscillator stage includes an RC type oscillator, wherein a certain number of resistors and/or capacitors can be selected by the random number introduced at the input of the oscillator stage so as to generate clock signals whose frequency depends on the RC component selected as a function of said received random number, and wherein a set of resistors is placed in series between a first current mirror, connected to a positive potential terminal of a voltage source, and a second current mirror connected to a negative potential terminal of said voltage source, the value of the resistor selected determining the value of the current to be duplicated in the first and second current mirrors.