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

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.

Dependencies are inferred from the claim text.