Abstract: A smart card and method of locking a smart card to block the operation of at least one protected program stored in a read-only memory or ROM of the smart card, the smart card incorporating a central processor, the ROM, an erasable programmable read-only memory or EPROM and a random access memory or RAM, the method comprising the steps of: entering a logic lock in the EPROM, making multiple copies of the logic lock in the EPROM, and carrying out a logic OR on the logic lock and the multiple copies in order to block the performance of the protected program upon the detection of either (a) the logic lock or (b) at least one of the multiple copies.

Abstract: The disclosure relates to chip cards and their functioning. When a chip card goes from a first state (A) to a second state (B), functions that were available in the first state are prohibited. To enable the analysis of the malfunctions of the card during a stage of qualification by the testing of an application under real-life experimental conditions, these functions need to be retrieved when a card suffers a malfunction. The invention proposes the placing, in the card, of two state indicators, the first indicator prohibiting the functions that are unnecessary for the step B and the second indicator checking the possibility of making the card return to the step A to retrieve the prohibited functions. The card reader may give the card a command for a return to the state A. This command is verified by the card. If the indicator is in a state that permits the return and if the command is correct, the first indicator is reset in the state corresponding to A. If not, the command is rejected.

Abstract: An integrated circuit, for use in a microprocessor-based chip card that provides several different functions at different hierarchical levels. The circuit has a microprocessor, a read-only memory managing a protection system and an EEPROM capable of containing not only data but also a code that can,be executed by the microprocessor. Different programs are placed in the EEPROM memory zones (Z1C, Z2C, Z3C). The read-only memory contains filtering instructions used to read a filter address in a specified zone Z1B, Z2B, Z3B of the EEPROM. Depending on the contents of this zone, the program will be routed, or not routed, towards the zones (Z1C, Z2C, Z3C). Thus information is recorded at only one address of the EEPROM in order to control accessibility to the different functions of the circuit.

Abstract: The method is designed to increase the protection of a microcircuit-based memory card comprising at least one memory coupled to a data-processing element. When said data-processing element receives a command by a data signal external to the card, said method consists in making said data-processing element emit a ratification signal at an instant that is deferred, with respect to the instant at which its emission was prompted by the data signal, by a duration that is randomly variable in time. The disclosed method can be applied to microcircuit-based memory cards.

Abstract: A method of locking a smart card to block the operation of at least one protected program stored in a read-only memory or ROM of the smart card, the smart card incorporating a central processor, the ROM, an erasable programmable read-only memory or EPROM and a random access memory or RAM, the method including the steps of: entering a logic lock in the EPROM, making multiple copies of the logic lock in the EPROM, carrying out a logic OR on the logic lock in the EPROM and the multiple copies of the logic lock in the EPROM in order to block the performance of the protected program upon the detection of either (a) the logic lock in the EPROM or (b) at least one of the multiple copies of the logic lock in the EPROM, recopying the logic lock in the RAM, and performing the logic OR on the logic lock in the EPROM, the multiple copies of the logic lock in the EPROM, and the logic lock in the RAM.

Abstract: The invention relates to integrated circuits and, notably, to circuits for which it is desired to provide security against any fraudulent usage. The circuits concerned are microprocessor circuits having a program memory, a programmable non-volatile memory, at least one input/output port and an RS register memorizing the signals from sensors of abnormal conditions. This register is accessible by the microprocessor. There is provision for means to check the state of the register immediately before any operation for the writing or erasure of the programmable memory, and immediately before any transmission of data towards the exterior of the input/output port, and means to interrupt the working of the microprocessor if the check reveals abnormal conditions.

Abstract: A method of ratifying secret codes for IC memory cards including a data processing member and a storage device for recording a secret code and data delivered to the card. It consists in determining at least one fixed-size memory zone in the storage device or systematically writing at least one bit in said zone prior to each presentation of a secret code, and in erasing all of the bits recorded in the fixed-size zone once the data processor member observes that the presented secret code corresponds to the secret code recorded in the card.

Abstract: To provide protection for the use of chip cards, the microprocessor of such a card is made, during the use of the card, to compute a signature according to complex encrypting algorithm taking account, firstly, of a secret code proper to the card and, secondly, of the instructions proper to the program. The signature thus computed is compared with a signature that has been pre-recorded in the card under the same conditions at the time of its delivery by the card-issuing party. It is shown that several uses can be authorized without jeopardizing their security.