Abstract: In a method for protected execution of a cryptographic calculation in which a key (12) with at least two key parameters (p, q, pinv, sp, dp, sq, dq) is drawn on, an integrity check (30, 34, 40, 54) of the key (12) is performed, in order to prevent a cryptographic attack in which conclusions are drawn as to at least one second key parameter (p, q, pinv, sp, dp, sq, dq) by corrupting at least one first key parameter (p, q, pinv, sp, dp, sq, dq). A further method serves to determine a key for a cryptographic calculation with at least two key parameters (p, q, pinv, sp, dp, sq, dq), provided for use in the first mentioned method. A computer program product and a portable data carrier have corresponding features. The invention enables particularly good protection of cryptographic calculations against attacks.

Abstract: The invention relates to a data storage medium having a semiconductor chip which has at least one memory in which an operating program is stored which contains a number of commands, with each command producing signals which can be detected from outside the semiconductor chip. According to the invention, the data storage medium is designed such that data which is used more than once for a calculation process is scrambled using different functions.

Abstract: The invention relates to a data storage medium having a semiconductor chip which has at least one memory in which an operating program is stored which contains a number of commands, with each command producing signals which can be detected from outside the semiconductor chip.