| 摘要 |
A control entity generates a set of control values for input to a processing entity that needs these control values for its proper working. The control entity can only generate the correct control values when enabled by an enabling entity, such as a smart card. The enabling and control entities each have a touch point word generator for respectively generating first and second identical successions of touch-point words. In addition, the enabling entity has a build-word generator for producing from each touch point word of the first succession, a corresponding build word having a value dependent on the value of the touch-point word concerned and its order position in the first succession. The enabling entity passes these build words to the control entity where they are used together with the corresponding touch point words of the second succession, to produce a series of command word values serving as the required control values. As the build words are of different values and are needed to generate the correct values, it is difficult for an attacker to modify the control entity in a way avoiding the need for the enabling entity to be present.
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