Encryption method for use with authentication of electronic devices, especially smart cards, whereby the exponentiation factor is protected by dividing it into two terms that are processed separately

摘要

Method for calculation of exponentiation within a group in order to authenticate a user of a physical device (U). Accordingly the exponent is decomposed into two terms, such that both terms must be known to determine the exponent. The first term is stored in device physical memory (H), while a pre-calculation is implemented whereby an element of the group is raised to the stored power with the result stored in a further memory (R). The final exponentiation calculation is undertaken using the value stored in memory (R) and a number determined from the second term. The invention also relates to a corresponding device.