Access control to data processing means

• US 20030188170A1
• Filed: 05/30/2003
• Published: 10/02/2003
• Est. Priority Date: 06/20/2000
• Status: Active Grant

• Current Assignee: Thales DIS France SA (Thales SA)
• Original Assignee: Gemalto SA (Thales SA)
• Inventors: Naccache, David, Guterman, Pascal, Rousseau, Ludovic, Bidan, Christophe, Girard, Pierre
• Granted Patent: US 8,583,934 B2
• Time in Patent Office: Days
• US Class Current: 713/182
• CPC Class Codes: G06Q 20/341 Active cards, i.e. cards including their own processing means, e.g. including an IC or chip
• CPC Class Codes: G07F 7/082 Features insuring the integrity of the data on or in the card
• CPC Class Codes: G07F 7/1008 Active credit-cards provided with means to personalise their use, e.g. with PIN-introduction/comparison system
• CPC Class Codes: G07F 7/1025 Identification of user by a PIN code

Abstract

The invention concerns a method aimed at preventing secret codes manipulations is a data processing means, such as a smart card (CA), by applying thereto a presented code. The method for accessing a functionality of the card comprises prior to implementation (E1) of a code transforming function (FT) in the processing means (CP), transformation (E2) of the secret code (CS) into a transformed secret code (CST) in the card. For each use of the card are provided transformation function, and a comparison (E7) of the transformed secret code with the transformed secret code in the card.

Claims

1. A method for accessing a data processing means (CA) associated with a secret confidential code (CS) and accessible by applying thereto a confidential code presented (CP) by an accepting means (TE), characterised in that it comprises the following steps:

first, implementation (E1) of a code transformation function (FT) in the processing means (CA), and then transformation (E2) of the secret code (CS) into a transformed secret code (CST) in the processing means according to the transformation function (FT) and storing (E3) of the transformed secret code (CST) in the processing means; and

at each use of the processing means (CA), transformation (E6) of the presented code (CP) into a transformed presented code (CPT) according to the transformation function implemented in the processing means, and comparison (E7) of the transformed secret code with the transformed presented code in the processing means.

2. A method in accordance with claim 1, according to which the transformation function is irreversible.

3. A method in accordance with claim 1 or 2, according to which the transformation function is a hashing.

4. A method in accordance with any one of claims 1 to 3, according to which each transformed code (CST, CPT) results from application of the respective confidential code (CS, CP) and a random number (NA) to the transformation function (FT), the random number (NA) being pre-stored with the transformed secret code (CST) in the processing means (CA).

5. A method in accordance with claim 4, according to which two data processing means (CA) associated with identical secret confidential codes (CS) are associated with different random numbers (NA).

6. A method in accordance with claim 4 or 5, according to which the random number (NA), is modified when the secret code (CS) associated with the processing means (CA) is modified.

7. A method in accordance with any one of claims 1 to 3, according to which the previously stored transformed secret code (CST) results from application of the secret code (CS) and a first random number (NA) to the transformation function (FT), a second random number (NA′

) is produced (E6a) in the processing means (CA) before each transformation of the presented code, then a second transformed secret code (CST′

) is determined by applying the stored transformed secret code (CST) and the second random number (NA′

) to the transformation function, and the transformed presented code (CPT′

) is determined by applying the presented code (CP) and the first random number (NA) to the transformation function in order to produce an intermediate transformed presented code (CPT) and applying the intermediate transformed presented code (CPT) and the second random number to the transformation function, the second transformed secret code (CST′

) being compared with the transformed presented code (CPT′

).

8. A method in accordance with any one of claims 1 to 6, according to which, for each presentation of the presented code, the following steps are carried out:

application (E6b) of the transformation function (FT) to the previously stored transformed secret code (CST<sub>i−

1</sub>);

applications (E6b) of the transformation function (FT) to the presented code (CP) as many times as the number of previous presentations of the presented code;

comparison (E7b) of the transformed secret code (CST_i) and the transformed presented code (CPT_i) resulting from the previous applications; and

storing of the transformed secret code (CST_i) in the processing means (CA).

9. A method in accordance with claim 8, according to which the applications of the transformation function to the presented code (CP) are replaced by an application of a transformation function equivalent to the i^th iteration of the transformation function (FT) in order to produce a transformed presented code (CPT_i) to be compared (E7b) with the transformed secret code (CST_i), and the number i of iterations is stored with the transformed secret code (CPT_i) resulting from the previous application in the processing means (CA).

10. A method in accordance with any one of claims 1 to 3, according to which the transformation function (FT) consists of dividing each code (CS, CP) into a number of parts and of applying a predetermined permutation to the parts of the code, and according to which, at each presentation of the presented code (CP), the permutation is applied to the transformed secret code (CST) resulting from the last presentation, the permutation is applied to the presented code a number of times equal to the number of previous permutations of the presented code, the corresponding parts of the permuted secret and presented codes (CST, CPT) are compared in pairs, and the permuted secret code (CST) is stored in the processing means (CA).

11. A method in accordance with any one of claims 1 to 10, according to which the transformation function (FT) to which there is applied the secret code (CS) is homomorphic of the transformation function (FT′

) to which there is applied the presented code (CP).