Protection of the core part of computer against external manipulation
AssigneeGiesecke & Devrient GmbH
InventorMichael Baldischweiler
Life of this patent
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Abstract
A method is proposed for protecting the central processing unit of a computer, in particular a smart card. Individual security-related registers are logically combined to form a check sum after the CPU has executed an instruction. The check sum is stored and compared with an accordingly formed check sum before the onset of processing of the next instruction. If the compared check sums fail to match, this indicates manipulation of the register contents of the CPU in the time period between the execution of the two instructions. In such a case a corresponding error message is issued and the processor stopped or the card confiscated.
Claims14
A method for protecting a computer with a central processing unit (CPU) and a clock signal supply providing a clock signal to the CPU from external manipulation, comprising the steps of:
- determining a final check sum by mathematical combination with reference to register contents of the CPU arising at the end of processing of an instruction by the CPU,
- storing the final check sum, and
- determining an initial check sum with reference to the register contents arising before the onset of processing of the next instruction by the CPU, and creating an error message if the initial check sum does not match the final check sum.
Dependencies are inferred from the claim text.