Reverse calculation circuit for chip card, has random number generator generating two random numbers, and inverter outputting number of bits expressing reverse elements of one set of elements of function

摘要

The circuit has a random number generator generating random numbers (R, m). An inverter (200) receives a number of bits that express elements (a(x)) and elements (p(x)) of a function as input data. The inverter outputs a number of bits expressing reverse elements (r(x)) of the element (a(x)), in response to the numbers (R, m). The random number (m) is greater than 3n and lesser than 2n, where n is the degree of the function. Independent claims are also included for the following: (A) a reverse calculation process (B) a computer readable storage medium on which a computer program is incorporated which implements a reverse calculation process.