Patent ID: 7602916

Claim:
A data carrier having a semiconductor chip with at least one memory containing an operating program which is able to carry out multiple executions of at least one operation (h), said multiple executions including a first execution of said operation (h) and at least one new execution of said operation (h), each of said multiple executions of the operation (h) requiring input data (x) and generating output data (y), characterized in that the operation (h) is disguised before each said new execution to obtain a new disguised operation (h R1 ) that is a different operation than the operation (h), and the new disguised operation (h R1 ) is executed with new disguised input data, wherein a random component is used in each new disguising of the operation (h) and the input data (x), and wherein each new disguising of the operation (h) and the input data (x) is coordinated such that the execution of the new disguised operation (h R1 ) with new disguised input data yields output data (y) identical with the output data (y) determined upon execution of the operation (h) with input data (x), whereby disguising said operation (h) before each new execution prevents analysis of said operation (h) and exposure of secret information about said semiconductor chip should a potential attacker intercept signal patterns generated during execution of said disguised operation (h R1 ).