Abstract: A secure information storage system in which a directory stores identifying titles and pointers to areas of a memory storing respective messages. To protect the messages against unauthorized changes, a MAC (message authentication code) is calculated for them in known manner and stored in a register in a secure unit. This involves processing the whole of each message every time the MAC is checked or, if a message has been changed, a fresh MAC has to be calculated. To avoid this, a separate MAC is calculated for each message and stored in the directory, and a global MAC is calculated for the individual MAC's (treating them as if they were a message) and stored in a secure register. To check a stored message, the global MAC is recalculated (thus verifying the MAC of the message), and the MAC of the message is recalculated (thus verifying the message). If the message is changed, its new MAC and a new global MAC are calculated. The system can be extended to a hierarchy of sub-global MAC's.

Abstract: The disclosure concerns the safety of the confidential information contained in integrated circuits. In a certain number of integrated circuit applications and, more particularly, in the circuits contained in cards known as "chip cards", it is necessary to prohibit access by unauthorized persons to confidential information stored in a memory of the circuit. To prevent the fraudulent practice of examining the current consumption at the terminals of the integrated circuit during an operation of reading or writing in the memory, a protection circuit is used. This protection circuit actuates the simulation, according to a pseudo-random sequence generated by a generator, of current consumption values identical to those of real memory cells.

Abstract: Filter networks are incorporated within a software protection hardware device which is plugged into a communications port of a computer which device will select bits or combinations of bits emanating from the communications port resulting from commands of a controlling software in use with the computer which is desired to be protected. The filter networks select the bits of a disguised predetermined control code which when matched with a stored reference code results in an output from the filter used to activate functions within the protection device. A stream of bits including a disguised predetermined control code issuing from the computer through the security device are compared with a stored reference code in a programmable memory. When a match occurs an output emanates providing an acknowledgment code to the computer indicating that the hardware device has been plugged in and is a proper one.

Abstract: Aircraft often include a central memory which distributes data to a number of communication, navigational and other utilization devices. In order to achieve a high degree of security for data transmission from the memory to the utilization devices, data subsets are distributed to the utilization devices in parallel so that any radiation generated from the parallel branches results in superposition of individual data signals. In effect, a jumbled resultant signal is produced which is difficult or near impossible for unfriendly surveillance equipment to decipher.

Abstract: A classification code, recorded repeatedly along with program material, is recovered on playing a video recording, and used to inhibit replay if the recovered code matches any of a set of codes specified by the user. The codes which cause replay to be inhibited can be set by the user after entering a personal identity number. The user can optionally request that a code be recorded when recording a program. Signals are optionally provided so that an auxiliary device, such as a second video player, can be controlled in response to codes recovered. One application is to prevent children viewing certain video recordings without parental permission.

Abstract: Pseudorandom pulse code generators utilize XOR gates constructed of a pair of back to back parallel connected laser diodes, and fiber optic delay lines connecting the XOR gates to generate PN code sequences with tens of Gbits/s data rates. The single tap generator uses a fiber optic line of a length representing a selected number of delay stages connected to the optical output of the XOR gate and with optical splitters at the end of the delay line and at a selected delay stage feeding back optical signals to the optical inputs of the XOR gate to produce the PN sequence at the end of the delay line. Multi-tap generators utilize additional electro-optical XOR gates connected in serial-parallel, or preferably in a converging cascade arrangement to feed back pulses to the delay line.

Abstract: A user controlled card computer C and communicating tamper-resistant part T are disclosed that conduct secure transactions with an external system S. All communication between T and S is moderated by C, who is able to prevent T and S from leaking any message or pre-arranged signals to each other. Additionally, S can verify that T is in immediate physical proximity. Even though S receives public key digital signatures through C that are checkable using public keys whose corresponding private keys are known only to a unique T, S is unable to learn which transactions involve which T. It is also possible for S to allow strictly limited messages to be communicated securely between S and T.

Abstract: In a multiparty verification system, a prover and a verifier are coupled to rocess respective outputs to provide a system output such as an identification verification. The prover is formed of plural units which share confidential information used to encrypt information carried by the prover. Communication between the prover units is prevented. The first prover unit encrypts the information based on additional information received from the verifier and transfers the encrypted information to the verifier. Subsequently, the verifier obtains from the second prover unit the shared confidential information required to decrypt a subset of the transmitted encrypted information.

Abstract: Apparatus and methods, readily adapted to interface with a standard data transmission network having an unsecure transmission channel, e.g., "Ethernet," for the provision of secure transmission of data over the network channel in a manner which is essentially transparent to the standard network devices and users, thereof, are provided. Various encryption keys are generated and utilized within the system to disguise or encrypt information transferrred between network nodes. The encryption keys are made known only to those network devices which are permitted to handle information encrypted with the encryption keys.

Abstract: An intelligent synchronous modem and data communication systems utilizing the intelligent synchronous modem are provided. The modem comprises: at least one connector having a first and a second port for primary and secondary channels of communication with a host computer, wherein the primary communication channel is for communication of synchronous data and the secondary communication channel is for communication of asynchronous data; a microprocessor for recognizing and executing commands of the host computer, wherein the commands are in the form of asynchronous data received over the secondary communication channnel; and interface means for interfacing the microprocessor with telephone lines, wherein synchronous data received by the microprocessor is sent to the interface means.

Abstract: A tracking receiver is disclosed which utilizes optical processing for detecting and tracking input broadband chirp like emission signals. The tracking receiver includes a scanning local oscillator, the output signal of which is caused to be scanned in frequency. A mixer mixes the unknown input signal and the local oscillator output signal to produce an intermediate frequency (IF), frequency difference signal. The IF signal is analyzed in an optical spectrum analyzer which includes an acoustooptical modulator for modulating a beam of radiation, as a laser beam, with the intermediate frequency signal, and optical means, as a lens, for producing a spatial frequency distribution of the intermediate frequency spectrum in a Fourier plane. A photodetector array is provided in the Fourier plane for detecting the spatial spectrum.

Abstract: A method and apparatus are provided for descrambling a sinewave scrambled television signal. The television signal is applied to a dual loop circuit that detects AM sinewave modulation on the television signal sound carrier. The detected modulation is applied to the picture carrier of the television signal in a first loop of the circuit to cancel the AM sinewave modulation therefrom. The detected modulation is applied to the sound carrier of the television signal in a second loop of the circuit to increase the AM sinewave modulation on the sound carrier within the loop. The net loop gain of the first loop is then lowered to minimize the application of noise from the sound carrier to the picture carrier.

Abstract: A secure Telephone Terminal apparatus and method is disclosed which permits clear analog or coded digital message signals to operate on a non-secure telephone network having conventional equipment. This Telephone Terminal is utilized as a Remote Interface at the location of each predetermined telephone subscriber authorized to receive and transmit coded message signals. Included within the Telephone Terminal is a telephone line interface, a telephone interface, a signal converting stage, and a mode selector, or controller. By utilizing a duplexer in the telephone interface and telephone line interface, the controller utilizes separate inbound and outbound signal paths to determine if a coded message signal is about to be received and switches the mode accordingly. This permits either subscriber to select the coded mode regardless of which subscriber initially set up the call.

Abstract: The thermal hysteresis of quartz crystal resonators is measured by exciting two modes of a quartz crystal of interest with an external frequency source at a preselected temperature, calculating the difference frequency as between the modes, resetting to the original set temperature after temporarily altering the temperature, remeasuring the frequencies while maintaining the temperature and the difference frequency at the same respective values as the original values, and taking the mode frequency difference as representative of the thermal hysteresis of the crystal.

Abstract: The invention provides a method of securing remote terminal access to a central computer. The method uses the services of a physically secure coprocessor which is, or will be, coupled to the remote terminal for the purposes of effecting remote access to the central computer. The method comprises transferring an encrypted decryption key from the central computer to the physically secure coprocessor. The coupling between the coprocessor and remote terminal allows a file to be encrypted which can confirm that the remote terminal (which is the source of the encrypted file) has or had access to the specific coprocessor to which the encrypted decryption key had previously been transferred. Thereafter the encrypted file is transferred to the central computer and is examined there to confirm that the source of the file has access to the specific coprocessor which received the encrypted decryption key.

Abstract: An intermediate scrambling device for a radiotelephone system is disclosed by which it is possible to establish and maintain scrambled communications between an originating scrambler terminal and the most distant companion scrambler on the circuit. The intermediate scrambler may establish and maintain the scrambled communications if it is the most distant scrambler, or it may become transparent to a more distant scrambler.

Abstract: A method for simplifying key management in situations where unique cryptographic keying relationships are required end-to-end between pairs of parties and a symmetric encryption algorithm is to be used. It is useful in cases where the parties come from disjoint subsets of the total population of parties. The method provides some of the characteristics of a public key crypto system (PKS) utilizing the public identities of the parties as part of the key, but lacks the property of PKS which allows a party to independently generate a secret key which is known only to that party.

Abstract: An interrogator-responder communication system in which responders are carried by vehicles (such as railroad vehicles) travelling along a route and in which an interrogating station situated along the route operates each passing responder to recall data from a memory in the passing responder. In one embodiment, the responder is equipped to receive data transmitted from a transmit station and to store the received data, for later recall, in a non-volatile, electrically erasable read/write memory.

Abstract: The portable electronic device (1) includes some optical reception devices (R), a microcomputer (4) suitable for processing the data received, a display device (6) to display data from the microcomputer (4), and an electrical energy source to supply the various circuits. The device includes a keyboard (8) which enables the user to also to key in data into the microcomputer (4), the latter being programmed to use the data from the optical reception devices (R) and/or from the keyboard (8), and to display results taking account of the data, possibly combined.

Abstract: The method in suitable for authenticating electronic memory cards intended for authorizing the supply of goods or services after being processed by a card reader machine. The card memory includes at least three zones (Z.sub.1, Z.sub.2, Z.sub.3) comprising a first zone (Z.sub.1) which is readable from outside and which contains information (I) and a corresponding signature (S) obtained by means of secret data (D) recorded in the third zone (A.sub.3) which cannot be read from outside the card. The second zone (Z.sub.2) which can be read from outside the card contains the result of secret key and public key encoding all of the data contained in the first zone. This method provides effective protection against several types of fraud.