METHOD FOR KEY DIVERSIFICATION ON AN IC CARD

• US 20080008315A1
• Filed: 06/29/2007
• Published: 01/10/2008
• Est. Priority Date: 06/29/2006
• Status: Active Grant

• Current Assignee: STMicroelectronics NV
• Original Assignee: Incard S.A. (STMicroelectronics NV)
• Inventors: Donatiello, Saverio, Fontana, Giovanni
• Granted Patent: US 7,894,601 B2
• Time in Patent Office: Days
• US Class Current: 380/044
• 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: G06Q 20/355 Personalisation of cards for use
• 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: H04L 2209/34 Encoding or coding, e.g. Huffman coding or error correction
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 9/0625 with splitting of the data block into left and right halves, e.g. Feistel based algorithms, DES, FEAL, IDEA or KASUMI
• CPC Class Codes: H04L 9/0866 involving user or device identifiers, e.g. serial number, physical or biometrical information, DNA, hand-signature or measurable physical characteristics
• CPC Class Codes: H04L 9/3273 for mutual authentication network architectures or network communication protocols for achieving mutual authentication in a packet data network H04L63/0869

Abstract

Key diversification is performed during a mutual authentication between a SAM integrated circuit (IC) card storing a master key, and a user IC card storing an identification number. The user IC card is connected to the SAM IC card through a communications interface. The key diversification includes deriving sub keys from the master key, and computing ciphered strings through corresponding cryptographic computations on a string obtained by an elaboration on the identification number with the sub keys. A diversification key is generated by linking together a combination of bytes of the ciphered strings.

Claims

1. Method for generating a key diversification during a mutual authentication between a master IC Card (1), storing a master key (K_M), and a User IC Card (2) associated to an identification number (ICC.SN), said User IC Card (2) being connected to said master IC Card (1) through a communication interface (ITF), the method comprising the steps of:

deriving at least a couple of sub keys (K_Ma, K_Mb) from said master key (K_M);

computing at least a couple of ciphered strings (A, B) through corresponding cryptographic computations on a string (T) with said sub keys (K_Ma, K_Mb), said string (T) obtained by an elaboration on said identification number (ICC.SN);

building a diversification key (K_ICC) concatenating a combination of bytes of said ciphered strings (A, B).

2. Method for generating a key diversification according to claim 1 characterized by the fact that said step of computing comprises a CRC operation (C) of said identification number (ICC.SN).

3. Method for generating a key diversification according to claim 2 characterized by the fact that said elaboration in said step of computing comprises a concatenation of said identification number (ICC.SN) with a fixed text string and/or a most significant bytes and/or a less significant bytes of said CRC operation (C).

4. Method for generating a key diversification according to claim 2 characterized by the fact that said bytes combination in said step of building said diversification key (K_ICC) comprises a XOR operation on said ciphered strings (A, B).

5. Method for generating a key diversification according to claim 1 characterized by comprising a step of adjusting a parity bit for said diversification key (K_ICC).

6. Method for generating a key diversification according to claim 1 characterized by comprising a step of adjusting at least a parity bit for said diversification key (K_ICC).

7. Method for generating a key diversification according to claim 1 characterized by the fact that said cryptographic computations in said step of computing comprises one or more DES computations.

8. IC Card, storing an identification number (ICC.SN), intended to be used in a communication session with a master IC Card, storing a master key (K_M), said IC Card being connectable to said master IC Card through an interface of communication, characterized by comprising means for:

deriving at least a couple of sub keys (K_Ma, K_Mb) from said master key (K_M);

computing a couple of ciphered strings (A, B) through a corresponding cryptographic computations on a string (T) with said sub keys (K_Ma, K_Mb) said string (T) obtained by an elaboration on said identification number (ICC.SN);

building a diversification key (K_ICC) concatenating a combination of bytes of said ciphered strings (A, B).