Security module for secure comparison of an authentication code with one stored in memory has additional auxiliary registers in which randomly chosen data words are placed for use in authenticating the code in the main registers

摘要

Procedure and device for comparison of a security code, such as a PIN, that is entered into some form of verifier with a code that is stored in secure memory. The device includes two extra auxiliary registers that are used with the main registers that the security code from secure memory and the code entered to be validated in a manner to prevent fraudulent discovery of the security code. Procedure for comparison of two registers involves use of two extra auxiliary registers in which a number of words (or bytes) are stored where the words are defined randomly by logic elements. A first sum is then calculated using these random values. The respective words in the main memory registers are compared two by two and then one of the words of the auxiliary registers is selected at random and modified by a first predetermined value if the main register words are the same and by a second predetermined value if the words are different. A second sum is then calculated using the auxiliary registers. This sum is then modified by a value equal to the first sum multiplied by the number of words in the main memory registers. When the two sums are equal the contents of the two main registers are the same, when different the main register contents are different.