Method for secure storage of sensitive data in a silicon chip integrated system storage in particular a smart card and integrated system therefor

• US 20020108051A1
• Filed: 02/08/2002
• Published: 08/08/2002
• Est. Priority Date: 06/08/2000
• Status: Active Grant

• Current Assignee: CP8 Technologies (Thales SA)
• Original Assignee: CP8 Technologies (Thales SA)
• Inventors: Hameau, Patricia, Fougeroux, Nicolas, Bole, Benoit
• Granted Patent: US 7,260,727 B2
• Time in Patent Office: Days
• US Class Current: 713/193
• 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

Abstract

The invention concerns a method for secure storage of a piece of so-called sensitive data, for example an encryption key, in a memory (M) of an embedded microchip system, particularly a smart card (CP). The memory (M) comprises two physically distinct storage devices (1, 2), for example a permanent memory of the “ROM” type (1), and a second, re-programmable memory of the “EEPROM” type (2). The piece of sensitive data is divided into at least two parts (d, d′), in a given logical configuration, each of these parts being stored in one of the distinct storage devices (1, 2). An additional piece of verification data, a checksum or hash data, can also be stored in the first storage device (1), at the same time as the first sensitive data part (d).

The invention also concerns an embedded microchip system, particularly a smart card (CP).

Claims

1. Method for secure storage of a piece of so-called sensitive data in a memory of an embedded microchip system comprising at least two physically distinct storage means, characterized in that said piece of sensitive data is divided into at least two parts (d, d′

), in a given logical configuration, and in that each of said divided parts (d, d′

) is stored in one of said physically distinct storage means (1, 2).

2. Method according to claim 1, characterized in that, said piece of sensitive data being divided into at least two parts (d, d′

), it constitutes a single secret, and in that each of said divided parts is stored in one of said physically distinct storage means (1, 2).

3. Method according to claim 1, characterized in that, said piece of sensitive data being divided into at least two parts (d, d′

), said first part (d) constitutes a first secret and each of said additional parts (d′

) are derived from said first part (d) so as to constitute additional secrets, and in that each of said divided parts is stored in one of said physically distinct storage means (1, 2).

4. Method according to claim 1, characterized in that said piece of sensitive data is a binary word with a length equal to a given number of bytes and is divided in order to be stored in two physically distinct storage means (1, 2), in that a first part is a first binary word (d) constituted by blocks of bytes (B₁-B₈) of the same length as said piece of sensitive data, in that said first part (d) includes a string of correct bytes and altered bytes (O₁-O₈), distributed in said word (d) in a predetermined configuration, and in that said second part is a second binary word (d′

) with a length equal to the number of said altered bytes (O₁-O₈) and constituted by bytes (O′

₁-O′

₈) that correspond one-to-one with said altered bytes (O₁-O₈), so that these altered bytes (O₁-O₈) can be corrected, and said piece of sensitive data can be reconstructed from said first (d) and second (d′

) parts.

5. Method according to claim 4, characterized in that said piece of sensitive data is an encryption key.

6. Method according to claim 1, characterized in that, said piece of sensitive data being divided into first (d) and second (d′

) parts, respectively stored in first (1) and second (2) physically distinct storage means, an operation called a checksum is performed on said sensitive data, concomitant with the storage of said second part (d), the result of which is in the form of a piece of informational data, in that said informational data is stored in said first storage means (1), and in that it includes a reading of said informational data, an additional checksum operation on said sensitive data, and a comparison between said informational data read and the result of said additional checksum operation with each use of said sensitive data, in order to certify its integrity.

7. Method according to claim 1, characterized in that, said piece of sensitive data being divided into first (d) and second (d′

) parts, respectively stored in first (1) and second (2) physically distinct storage means, an operation called a hash is performed on said sensitive data, concomitant with the storage of said second part (d), the result of which is in the form of a piece of informational data (H), in that said informational data (H) is stored in said first storage means (1), and in that it includes a reading of said informational data (H), an additional hash operation on said sensitive data, and a comparison between said informational data read and the result of said additional hash operation with each use of said sensitive data, in order to certify its integrity.

8. Method according to claim 7, characterized in that said hash operation is obtained by applying the hash algorithm known as “

SHA-1”

to said piece of sensitive data.

9. Embedded microchip system equipped with storage means for storing at least one piece of so-called sensitive data, said storage means comprising at least two physically distinct storage devices, characterized in that, said piece of sensitive data being divided into at least two parts (d, d′

) with given configurations, each of said storage devices (1, 2) stores one of said parts of sensitive data (d, d′

).

10. System according to claim 9, characterized in that said storage means (M) comprise a first read-only storage device of the so-called “

ROM”

type (1), and a second electrically erasable re-programmable read-only storage device of the so-called “

EEPROM”

type (2), and in that each of said first (1), and second (2) storage devices store one of said divided parts (d, d′

) of said piece of sensitive data.

11. System according to claim 9, characterized in that it is constituted by a smart card (CP).