A method of unlocking the anti-starting system of a computer (ECM) controlling the operation of an engine of a motor vehicle, includes: each time the computer is powered up generating therewith a first random value and writing the value into a first zone of a volatile memory of the computer, downloading an unlocking program from a downloading tool to the volatile memory, the execution of which generates the calculation of a second value from the first random value and from a determined relation stored in the unlocking program, and writing the second value into a second zone of the volatile memory of the computer, reinitializing the software of the computer without erasing the first and second zones of the volatile memory of the computer, comparing the values stored in the first and second zones, unlocking the anti-starting system of the computer, if the comparison is successful.