Method for generating a random number in a data processing system/and system for implementing the method
AssigneeBull CP8
InventorMichel Hazard
Life of this patent
Estimating the term…
Abstract
In a data processing system using portable objects (1) such as cards incorporating memory chips (11, 12, 13, 14, 15) and a processing circuit (10), where a first memory zone (11) is electrically erasable and writable at the request of the processing circuits in the object, random numbers are generated taking into account a first parameter taken from the first zone (11) and at least one second parameter written in a second, nonvolatile zone (12) of the object, the content of this second zone being modified each time the first zone is erased such that the combination of parameters is never identical following the various erase operations on the first zone.
Claims22
A method of generating a random number (RND) in a data processing system, employing at least one portable object (1) including processing circuits (T1) and at least one first memory zone (11) that can be written to and is capable of being erased on a request from the processing circuits (T1) of the portable object, the method comprising causing at least a first parameter (X) contained in the first memory zone to be taken into account, and being characterized in that it consists in causing at least one second parameter (Y) written in a second non-volatile zone (12) of the portable object, to be taken into account, in combination with the first parameter (X), to calculate the random number, and that the contents of the second zone are modified by the processing circuits of the object each time the first zone is erased, such that in the event of, or after, such an erasure, the first parameter (X) resumes a value identical to a value that it would have had between the first time the portable object was put into service and the most recent erasure.
The method of 1 or 2 claims, characterized in that the second zone (12) comprises words that are each locatable by an address and each contain a predetermined number (n) of bits, and that the second parameter (Y) comprises the last modified word of the second zone and the address of this word.
A system for implementing the method of generating a random number (RND), characterized in that it includes at least one portable object (1) adapted to be coupled temporarily to a terminal (2), the portable object having processing circuit means and at least one first electrically writable, erasable and programmable memory zone (11), and at least one second non-volatile memory zone (12) that can be written under the control of the processing circuit means (T1) of the portable object, when the first zone (11) is modified, in such a way as to be capable of causing at least one random number to be developed in the object, in each current session in which the portable object is connected to the terminal, by a calculation taking into account at least one first parameter (X) sampled in the first zone (11) and modified in each session and at least one second parameter (Y) sampled in the second zone (12) and modified upon each erasure of the first zone.
Dependencies are inferred from the claim text.