Abstract: A system and method are disclosed for preventing intelligible interception of information signals transmitted over a two-direction line. A masking signal is applied through a hybrid circuit at the receiving end of the line, and this masking signal, which appears on the line together with the information signal, prevents the intelligible decoding. Only at the receiving end of the line, where the hybrid circuit attenuates the masking signal which it receives at its receive port, can intelligible decoding take place. Signal processing techniques used at the receiving end permit larger amplitude masking signals to be used, thus creating even greater confusion for an unauthorized detecting mechanism which is coupled to the line.

Abstract: The cryptographic system comprises at least one encryption station, one decryption station and a trapdoor generator. The trapdoor generator comprises means for selecting r distinct prime numbers pi, generating a modulus m that is a product of the prime numbers pi, selecting a pair of integers (a,b) satisfying 0.ltoreq.a<m and 0.ltoreq.b<m, computing for each pi a number N(pi) of distinct pairs of integers (x,y) satisfying 0.ltoreq.x<pi and 0.ltoreq.y<pi and y.sup.2 .ident.x.sup.3 +a.multidot.x+b (mod pi) and a sum N(pi)+1 representative of an order of an elliptic curve defined as the set of pairs of integers (x,y), computing a least common multiple .mu. of the values N(pi)+1, selecting a public multiplier e relatively prime to .mu., computing a secret multiplier d according to d.ident.1/e (mod .mu.), and transferring data comprising at least m, a, b and e to a storage means provided in the cryptographic system.

Abstract: A method of remotely changing an original voice encryption key in a secure radio (10) is provided which includes a central controller (20) transmitting to the secure radio a digital word (42) representing a selective operation to be performed on the original voice encryption key stored in the radio (10). In response to the digital word (42), the radio (10) performs the operation on the original voice encryption key to generate a current voice encryption key.

Abstract: Access to a vehicle by a remote electronic key via a radio link is secured by an exchange of encrypted signals. A remote unit having a secret number is introduced to a base unit and a common key is agreed upon by an exponential key exchange. The common key is encrypted using the secret number and stored in the base unit. Thereafter, the base unit is able to authenticate the identity of the remote unit by sending the encrypted common key and a random number to the remote unit which decrypts the key and uses it to encrypt the random number. The random number is also encrypted in the base unit and compared with the encrypted random number from the remote unit.

Abstract: A system for securely providing restricted information having an encoder for transmitting selected update data with respective keys and a plurality of uniquely identified decoders for receiving said update data. When saidd decoder matches the key sent with said update, said decoder receives the update data and appropriately positions said update data in respective pages in a store for subsequent viewing on a video display.

Abstract: A device is disclosed for controlling access to cable television signals. Jamming oscillators are shifted in frequency, jamming multiple services each. The oscillators are shared between multiple subscriber ports, providing a cost effective, high security control system. A modular approach allows security to be added as additional capacity is required.

Abstract: According to the invention, on the emitter side, a number generator (10) delivers a random code (XAL) which is sent to the input of a master card (11) which ciphers such code according to a predetermined key (100), the code thus ciphered is broadcast with the video signal, a first device (17) receives, on the one hand, the random code (XA) and, on the other hand, the code ciphered by the master card (11) and effects a predetermined numerical combination of these two codes, such combination forming the initialization word of a pseudo-random generator (12) intended to provide a table of codes for scrambling the video signal and, on the receiver side, the ciphered code received is deciphered by a customer card (13), a second device (18) receives at the inputs, on the one hand, the ciphered code and, on the other hand, the code deciphered (XA) by the customer card (13) and effects a numerical combination of these two codes which is similar to the combination of the first device (17).

Abstract: Apparatus for defeating a noise inverter disposed within the IC includes circuitry for changing the amplitude of the AGC signal applied to an AGC amplifier prior to the noise inverter so as to lower the level of the signal fed to the noise inverter. As a result, the signal fed to the noise inverter is less than the threshold signal level necessary for operation of the noise inverter. This enables use of an EIA multiport standard decoder with a standard television signal processing IC wherein the noise inverter is not directly accessible for defeating it.

Abstract: A local area network (10) utilizes a wireless transmission link and has network stations (12) each having two differently polarized antennas (14, 16). Data transmission utilizes a spread spectrum code and in the receiver, correlator outputs are utilized in an integrator and registers circuit (54) to provide correlator output sample values integrated over a plurality of symbol intervals. These values are stored in registers (156) the contents of which are utilized to determine a peak value and a total value which are applied to a spike quality determination circuit (78) including a look-up table (200). The resultant spike quality output value represents the quality of the received signal and is utilized for carrier detection and for antenna selection.

Abstract: A method and apparatus for determining a change in velocity of a body following a power disruptive event. An accelerometer (10, 50) includes quartz crystals (16 and 18, 60 and 62), which produce output signals indicative of the acceleration to which a body connected to the accelerometer is subjected. The acceleration measured is directed along the sensitive axis of the accelerometer. The quartz crystals are selected to have different scale factors, K.sub.1 and K.sub.2, which define the change in frequency of the quartz crystal from its no-load resonant frequency as a force is applied to it. The quartz crystals are connected between a supporting case (14) and a proof mass (12) so that a given acceleration applied to the proof mass along its sensitive axis causes one of the crystals to experience a tension force and the other to experience a compression force.

Abstract: A local area network station for receiving data symbols encoded in a spread spectrum code and transmitted over a wireless channel includes in-phase and quadrature correlators (42, 44) the output signals of which are used to address a look-up table (50) for conversion to amplitude and phase sample signals. Corresponding amplitude sample signals are integrated and stored in a plurality of registers (96) and for each symbol, the register (96) storing the maximum value is ascertained to identify the associated sample number, which is stored in a sample number register (160). This sample number is utilized to determine the time of a symbol clock signal (RXCLK) used for clocking the received data.

Abstract: A data encryption device with a plurality of data encryption boards for encrypting data is provided. In a preferred embodiment, the data encryption device has a monitor processor connected to a parallel bus. Each data encryption board has a parallel port for connection to the parallel bus and a serial port for connection to a host computer. Each data encryption board operates independently of the other data encryption boards. A plurality of data encryption boards may be connected to the bus. In operation, a host computer sends data to a data encryption board. The data encryption board encrypts the data and sends the encrypted data to the host processor. The monitor processor and the data encryption boards are preferably in the same housing unit with a tamper detection mechanism.

Abstract: A television scrambling system of the GSS type includes a false key signal to defeat pirate decoders. The false key is placed approximately one half a horizontal line period following the last horizontal sync pulse preceding the vertical blanking interval of the television signal. If the pirate decoder is set to attenuate the video portion of the picture signal in response to receipt of a standard GSS scrambled signal, the pirate decoders will attenuate only the sync portion of the picture signal in response to a signal scrambled with the false key.

Abstract: An efficient software protection scheme is presented in which a data processing system provides comprehensive software protection using hardware and software measures. Specifically, it provides protection of the pattern of access to memory during execution of a program and also provides protection of the data stored in memory. The protection scheme is secure in the sense that it behaves like a black box which reveals no information other than the I/O behavior and running time. Thus, not only the values stored in the general purpose memory are hidden, but also the sequence in which memory location are accessed during execution is hidden. This comprehensive scope of protection is achieved by an extremely efficient scheme. In particular, if the running time of the original program it T, the running time of the protected program is only slower by some factor of (logT).sup.C where C is a small constant.

Abstract: A spread spectrum receiver using a correlator is disclosed, in which first and second comparing means comparing a correlation spike coming from the correlator with a first and a second reference voltage are used, the reference voltages being regulated, depending on the output of the first comparing means so that variations of the correlation spikes are followed precisely to obtain a two-valued correlation pulse.

Abstract: A radar processor is described which performs acceleration compensation for accelerating targets. A set of matched filters is formed that compensates for each one of a predetermined set of target accelerations. The matched filters optimize the signal-to-noise ratio by weighting and combining the Doppler filters over which the target is spreading. As a result, enhanced detection capability of maneuvering targets that spread their energy over Doppler filters is provided. Radar processor loading is reduced, thus making practical the implementation of long coherent arrays.

Abstract: A cipher system is disclosed in which each character of a plaintext alphabet has associated with it a randomly distributed collection of integers of a given length. These collections of integers are secretly shared by a sender and receiver pair. The plaintext characters of a message are sequentially coded by randomly selecting representatives from the integer collections corresponding to the plaintex characters. To this sequence of concatenated integers, regarded as a single integer, is added a random integer of length equal to that of the coded-for-message integer stiring. This random integer is taken from a random digits shared by the sender and receiver. The indexing of the random integer in the digit string is transmitted as part of the cryptogram. The summed random integer plus the coding integer string is transmitted as the body of the cryptogram.

Abstract: In a CATV terminal or a video apparatus such as a TV receiver, noises superimposed on a DC part of a horizontal synchronizing signal of a video signal are eliminated by integrating the DC part or replacing the DC part with an appropriate constant voltage. Noises superimposed on a back porch portion of the video signal are eliminated in the similar manner by subjecting a luminance signal which has been separated from the video signal to the noise eliminating operation.

Abstract: A cable television reverse manifold system is coupled between first and second diplexers of off-premises subscriber service providing equipment. The diplexers separate the transmission path between a headend and a subscriber into downstream or forward and upstream or reverse transmission paths. In one embodiment, the reverse manifold apparatus combines signals from at least one subscriber for transmission to the headend. In another embodiment including a data receiver and a controller, the off premises service providing equipment may be controlled by the subscriber. In yet a third embodiment, a radio frequency transmitter is coupled between the controller and the upstream diplexer which may actuate a plurality of simultaneous data transmissions over separate data channels in the notoriously noisy subsplit 5-30 megahertz transmission spectrum.

Abstract: A method and corresponding apparatus for encoding and decoding additional status bits into an existing frame status byte transmitted as part of a packet of information in a communication network. The described scheme provides for the encoding and decoding of two additional status bits, without having to modify the packet format. In the disclosed embodiment of the invention, the additional status bits are used to convey information to a node processor concerning decryption processing of a received information packets.