Abstract: The MOS cell with adjustable threshold voltage is a cell of the type with a memory that is electrically-erasable and programmable by storage of charges by tunnel effect in a floating gate. To obtain a circuit with adjustable threshold voltage, the cell is first of all "programmed" at zero so that all the charges that may be stored are removed and then it is "erased", with its source grounded, its drain taken to the high potential and its control gate taken to the potential desired for the threshold voltage V.sub.T of the circuit. At the end of this phase, the threshold voltage is adjusted. This device can be applied notably to circuits requiring precise voltage references in MOS technology, namely circuits of the detector or analog-digital converter type.

Abstract: The disclosure relates to counters that require the counting to be done under conditions of high security. In such a counter, starting from a number represented by a certain number of bits, the stages of the counter are successively forced, one after the other, to represent the final number in an order such that at no instant do the contents of the counter represent a number smaller than the initial number. A particular structure is used to count very big numbers while, when the technology is of the EEPROM type. This prevents the stage that changes its state most frequently from being subjected to action more than is physically permitted by the technology used. The disclosed method makes it possible, in chip cards, to prevent the diminishing of memorized values representing substantial values which are, for example, monetary values.

Abstract: The invention relates to exchangeable memory cards having several integrated circuits for personal computers. These memory cards serve as a large capacity mass memory for replacing floppy disks and other exchangeable magnetic supports. In particular, they have a plug-in connector (12) at the end of the card and can be inserted in the reader in accordance with PCMCIA standards of a micro-computer. According to an aspect of the invention, a flush contact chip card memory is formed by such a plug-in card (10) and for this purpose the latter has a supplementary connector with flush contacts on its principal face (14). The thus formed reader is transportable, with its application software stored in the card (10) and can be installed in any random microcomputer equipped with a PCMCIA reader. A credit card or security card (18) can then be inserted in the transportable reader. The memory card is typical a PCMCIA size card with a recess on one major plane surface and the security card fits into this recess.

Abstract: Disclosed is a method of authentication of data elements of the type that may be needed, for example, to authenticate a chip card before permitting a transaction instrument to deliver a service to the holder of this card. Should the authentication consist in ascertaining that an information content is truly present in the card at a determined address of a memory of the card, it is proposed to make the length of the block of information elements parametrizable and to include, in the algorithm for the encryption of this block, data relating to this length; the logic address of the file that contains the block and the position of the block in the file are also used. Furthermore, preferably a recursive algorithm is performed in N steps: the block to be authenticated is sliced into slices of fixed length and, at each step, the Exclusive-OR function of a slice considered and of the result of the preceding step is used as the data to be encrypted. FIG. 1.

Abstract: The invention concerns interface circuits for chip card readers. It consists of providing link connections between this circuit and the reader, these connections being identical to those established between the circuit and the chip card. An internal switch (102) in the circuit is used to link these connections together, or to a control register (101), which is internal to the circuit, and actuated by an additional control connection. With the invention, it is possible to limit the number of connections between the circuit and the reader and to control the circuit with a software interface which is identical to the control interface of a chip card.

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: A MOS fuse with oxide breakdown based on a MOS cell electrically programmable by tunnel effect and storage of charges at a gate. This cell is converted into a fuse by providing for the application, when the fuse has to break down, of an intense field, greater than the oxide breakdown threshold, in the tunnel window. Thus, the breakdown is irreversible. The disclosed device can be applied notably to fuses designed for the integrated circuits of memory cards.

Abstract: The disclosure concerns memory cards and, more particularly, cards that are used as means of prepayment in installations for the dispensing of products and services. It is proposed to make the memory rechargeable by means of a credit counter, incrementable from outside the card, and a comparator which compares the content of this counter with that of a page counter. The page counter records the number of pages of P accounting units already used up. A no more credit signal is emitted on an external terminal when the content of the page counter reaches the content of the credit counter. A security system against the fraudulent recharging of the card is set up by an algorithm bringing into play the content of the credit counter and an identification number contained in the card.

Abstract: The method for the management of transactions in a system including card readers and the associated microcircuit cards consists in organizing the memory of the cards, designed for the recording of the transactions, in two zones, one zone that is accessible through the presenting of the bearer code at each transaction, for the transactions involving sums above a predetermined value, the other zone being accessible for the transactions involving sums that are below the predetermined value, without any systematic presenting of the bearer's code: a presenting of the bearer's code commands the writing of opening bits of recording spaces in this second zone until the number of open spaces is equal to N which is a predetermined value. The disclosed method can be applied, notably, to credit cards, telephone cards and multiple-use cards.

Abstract: To provide I.C. cards that are reinforced and above all in which the card body is compatible both with using the I.C. in the card and with using a surface of the card that is coated with a film of magnetic material, at least two reinforcing sheets made of different types of reinforcing material are provided so as to adapt the expansion coefficient and the strength coefficient of the card so that both these coefficients lie within a range that is common to both card technologies. It is shown that this provides greater synergy in use of cards having both electronic memory and magnetic memory since in spite of temperature expansion magnetic card shapes are maintained, thereby making it possible to use magnetic tracks that comply with mass data storage requirements for use with magnetic tracks.

Abstract: The method of loading applications programs into a memory card reader having a microprocessor, connected by telephone to a server center, and suitable for executing these applications is such that the applications programs are stored in the memories of cards entitled to said applications while corresponding application pointers are stored in the server center, with the method consisting, once a card has been inserted in the reader, in setting up a telephone call from the reader to the server, in transferring the pointer for the application requested by the reader over the telephone line, in the reader interpreting the pointer to find the corresponding application program in the card, and then in transferring the program very quickly to the reader for the purpose of executing it. The invention applies in particular to those applications programs which are run most frequently from a memory card.

Abstract: To avoid the need for making microprocessor-fitted bank cards which, although they cost little, are in a relatively far too expensive range, money cards with only memory zones are made. They then have four memory zones, one zone pertaining to the identity of the bearer or to that of the card, one zone pertaining to the financial balance, a third zone pertaining to an interaction counter. This interaction counter counts the number of financial operations performed with the card. A fourth zone includes a certificate. This certificate is prepared, in each reader that performs a transaction with the card, with a DES algorithm. The value of this certificate is a function, according to an algorithm common to all the readers, of the identity, the content of the interaction counter and the balance. When a new operation is performed with the card, it is ascertained beforehand that the content of the certificate is the same as the one that can be recomputed by any terminal provided with the same algorithm.