Device for the protection of access to a permanent memory of a portable data carrier

• US 4,295,041 A
• Filed: 04/07/1980
• Issued: 10/13/1981
• Est. Priority Date: 08/26/1977
• Status: Expired due to Term

• Current Assignee: Compagnie Internationale Pour L'Informatique Cii-Honeywell Bull
• Original Assignee: Compagnie Internationale Pour L'Informatique Cii-Honeywell Bull
• Inventors: Ugon, Michel
• Primary Examiner(s): Pitts, Harold I.
• Application Number:
  US06/137,973
• Time in Patent Office: 554 Days
• Field of Search: 235/487, 235/488, 235/419
• US Class Current: 235/487
• CPC Class Codes: G06F 21/755 with measures against power attack
• CPC Class Codes: G06F 21/79 in semiconductor storage media, e.g. directly-addressable memories
• CPC Class Codes: G06F 21/80 in storage media based on magnetic or optical technology, e.g. disks with sectors preventing unauthorised reproduction or copying of disc-type recordable media G11B20/00
• CPC Class Codes: G06F 2221/2121 Chip on media, e.g. a disk or tape with a chip embedded in its case
• CPC Class Codes: G06K 19/073 Special arrangements for circuits, e.g. for protecting identification code in memory protection against unauthorised use of computer memory G06F12/14
• CPC Class Codes: G06K 19/07363 by preventing analysis of the circuit, e.g. dynamic or static power analysis or current analysis
• 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 20/357 Cards having a plurality of specified features
• 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 7/1083 Counting of PIN attempts
• CPC Class Codes: G11C 16/22 Safety or protection circuits preventing unauthorised or accidental access to memory cells

Abstract

A portable data or information carrier in the form of a card or the like. In order to maximize the confidentiality of information stored in the carrier, and more specifically to limit the amount of information available to a would-be defrauder monitoring data lines connecting the data carrier to external devices, the data carrier includes a microprocessor and an operatively associated protected memory to which access is protected. The memory includes at least one key or code which is compared to a key received from a device external to the data carrier to determine whether a particular operation is authorized. To ensure that the data carrier consumes the same amount of current whether the requested operation is authorized or unauthorized, the data carrier includes "access" and key "error" memory elements of the Electrically Alterable Read Only Memory (EAROM) type, and a bit is stored in the respective memory element in either event.

Claims

1. A portable data carrier for storing and processing data, comprising:

a microprocessor;

a protected memory to which access is to be protected;

an access memory element of the electrically alterable read only memory type and an error memory element of the electrically alterable read only memory type;

said microprocessor including internal first elements for reading and writing in said protected memory, second elements for receiving external data to be written in said protected memory, and third elements for externally transmitting data read from said protected memory; and

said internal first elements including means for checking an enabling key received from a device external to said carrier, means for storing an error bit in said error memory element when the enabling key is incorrect, and means for storing an access bit in said access memory element when the enabling key is correct.

2. A portable data carrier according to claim 1, wherein said means for storing an access bit in said access memory element areases said access memory prior to such storing.

3. A portable data carrier according to claim 2, wherein said means for storing an error bit in said error memory element erases said error memory prior to such storing.

4. A portable data carrier according to claim 1, wherein said internal first elements further include means for counting and storing in said access and error memory elements respective accumulated counts of accesses and access key errors.