Method for determining source output data from source input data based on a cryptographic operation modifies a cryptographic operation according to forward/reverse-modifying rules.

摘要

A cryptographic operation is altered according to a forward-modifying rule (120) in order to get an altered cryptographic operation (ACO) (110), which is executed to get output data for the ACO. Source input data (500) or output data for the ACO is changed (170) to get source output data (520), to be precise subject to a reverse-modifying rule (180). The reverse-modifying rule is adapted to the forward-modifying rule and defined so that the altered cryptographic operation (ACO) delivers the source output data (SOD) together with modified source input data or so that the ACO delivers the SOD together with modified output data for the cryptographic operation or so that the ACO delivers the SOD together with modified source input data and modified output data for the cryptographic operation. An Independent claim is also included for a device for determining source output data from source input data based on a cryptographic operation.