Abstract: A method, arrangement, and apparatus for providing an authentication to an application provided through a communications network. A connection is established between the application and a user interface through said communications network so as to enable an access of a user to the application. An authentication is provided to said application by means of a mobile station communicating through a mobile communications network.

Abstract: An arrangement for providing secure transmission of information. The bulk of the information is transmitted over non-secure channels such as broadcast media which terminate on a plurality of receiving stations. However, a residue of data is transmitted over a protected channel, such as a point-to-point channel, established for example, by a telephone connection. Interception of a complete message, when only the bulk of the message is available, becomes very difficult. It becomes even more difficult if scrambling arrangements are used to select the particular bits of the data message that are transmitted over the secure channel. It becomes still more difficult, if the data transmitted over the secure channel, itself, alters the scrambling algorithm.

Abstract: The present invention provides a data transmission apparatus which enhances the safety with respect to leakage of encoded transmitted data by raising the safety of transmission of an encoding key or a decoding key. It provides a large capacity transmission line 152 such as a satellite transmission line for transmitting a large amount of data and a small capacity transmission line 156 such as a public telephone line for transmitting an encoding key or decoding key or information for the generation of them. The encoding session key 107 is generated by using a work key and a destination address of a receiving apparatus of the destination. Further, the decoding session key 108 is generated using one's own address and the work key. The work key is preferably encoded and transmitted through the small capacity transmission line 156.

Abstract: A cryptographic device includes a de-multiplexer, a plurality of encryption blocks, a plurality of permutation blocks, and a multiplexer. The encryption blocks encrypt data to produce encrypted data. The de-multiplexer receives data portions from a plaintext message and directs the data portions to one of the encryption blocks, based on a value within a path control session key. Each permutation block is associated with an encryption block. Each permutation block permutes encrypted data from the encryption block associated therewith. The multiplexer receives data portions from each of the plurality of permutation blocks to produce an encrypted output data stream.

Abstract: The downlink channelization code limitation problem encountered in spread spectrum or CDMA cellular systems is resolved by using codes from a different, non-orthogonal code set when operating in the slotted mode. The non-orthogonal code sets can be constructed by using the same channelization code tree, but applying a different scrambling code.

Abstract: In a network communications system involving a Customer, a Retailer and a acquirer (for example credit-card provider). The method includes a six step procedure for providing a secure way of making network transactions, by providing complete isolation between the customer's full details, needed to complete a transaction, and the retailer or any other third side trying to get access to them by splitting this information to two parts, each transferred in a sperate line of transmission, one between the customer-retailer and the second between the customer and the credit card provider, and when one of them includes initiated response to the consumer, by the acquirer. By doing so living the sole control of data in the acquirers (for example Issuer) secured server.

Abstract: The present invention provides a data transmission apparatus which enhances the safety with respect to leakage of encoded transmitted data by raising the safety of transmission of an encoding key or a decoding key. It provides a large capacity transmission line 152 such as a satellite transmission line for transmitting a large amount of data and a small capacity transmission line 156 such as a public telephone line for transmitting an encoding key or decoding key or information for the generation of them. The encoding session key 107 is generated by using a work key and a destination address of a receiving apparatus of the destination. Further, the decoding session key 108 is generated using one's own address and the work key. The work key is preferably encoded and transmitted through the small capacity transmission line 156.

Abstract: A system and method implemented in an interactive television system for restricting or controlling the access rights of interactive television applications and carousels. The system broadcasts modules from a broadcast station to a plurality of receiving stations, which execute applications containing the modules. In one embodiment, the applications utilize a credential consisting of a producer identification number (ID) and an application ID for each of the grantor and grantee applications, an expiration date, a set of permission data, a producer certificate and a signature. An application requesting access and a carousel granting access may be identified by respective producer and application IDs. The credential utilizes public key encryption to ensure the integrity of the credential. The producer and application IDs may be replaced with wildcards so that rights may be granted to a group of producers or applications.

Abstract: A state synchronized cipher text scrambler is disclosed. The state synchronized cipher text scrambler enables multiple data streams to be scrambled in parallel in such a way that the data streams are uncorrelated with respect to each other and there is a large fixed delay relationship between the scrambler bits over the multiple streams. This enables a receiver to correctly identify the ordering of the multiple data streams with respect to each other automatically, correct for any polarity or wire-swap misconnections and align the received multiple data streams despite differential delays between the data streams.

Abstract: An encryption chip is programmable to process a variety of secret key and public key encryption algorithms. The chip includes a pipeline of processing elements, each of which can process a round within a secret key algorithm. Data is transferred between the processing elements through dual port memories. A central processing unit allows for processing of very wide data words from global memory in single cycle operations. An adder circuit is simplified by using plural relatively small adder circuits with sums and carries looped back in plural cycles. Multiplier circuitry can be shared between the processing elements and the central processor by adapting the smaller processing element multipliers for concatenation as a very wide central processor multiplier.

Abstract: The invention relates to a method of providing connection security for a connection between terminals in a wireless network. In the method data is transmitted from a first terminal (MS1) via nodes in the network to a second terminal (MS2). The method according to the invention is characterized by that it includes the steps of: routing the transmitted data via a mediator (MD), using the first security method for providing connection security at the security protocol layer between the first terminal (MS1) and the mediator (MD), using the second security method for providing connection security at the security protocol layer between the mediator (MD) and the second terminal (MS2), and performing the security method conversion at the security protocol layer at the mediator (MD).

Abstract: A networked catalog search, retrieval, and information correlation and matching system is disclosed. The system allows suppliers to publish information in electronic catalogs, structure the information in an object oriented representation distributed across a network of computers, for example, the Internet. The system also enables customers to search and retrieve information on products and suppliers which match dynamically specified customer requirements. Through retrieving compliant HTML pages, a search engine forwards retrieved pages to an object oriented database which sorts received information by the information's internal organization structure. By searching the information as stored in the knowledge base, a user may quickly retrieve the stored information as highly tailored to the user's search strategy. Also, additional tools operate on the stored information so as to, inter alia, organize design trades between selected elements where additional design and selection options are provided to each user.

Abstract: A system and method implemented in an interactive television system for restricting access between modules of different interactive television applications and carousels. The system broadcasts modules from a broadcast station to a plurality of receiving stations, which execute applications containing the modules. The applications utilize a credential consisting of a producer identification number (ID) and an application ID for each of the grantor and grantee applications/carousels, an expiration date, a producer certificate and a signature. A application requesting access (grantee) and a carousel granting access (grantor) are each identified by respective producer and application IDs. The credential utilizes public key encryption for ensure the integrity of the credential.

Abstract: The present invention relates to electronic monetary systems in general, and in particular to measures for making their use easier for an average user. The present invention is based on the idea that the use of electronic money is greatly simplified for a non-expert user, if the Internet Service Provider of the user takes care of the payments, and adds corresponding charges on the user's telephone bill. Such functionality requires the intervention of the ISP in the transmissions between a user and a third party, i.e. intercepting the electronic payment requests sent by a merchant. According to the present invention, the ISP uses electronic money on behalf of the user, and charges the payments on the user's telephone bill. The ISP can take care of all technical details necessary for obtaining different forms of electronic money in a centralized manner, and all users of the ISP can use the electronic money obtained by the ISP simply by allowing the ISP to add corresponding charges to their telephone bills.

Abstract: A method for performing secure transactions, such as credit card purchases, using two or more non-secure networks (such as the Internet and the public telephone system) in such a way that security is insured. A person wishing to initiate a secure transaction sends a message over one of the non-secure networks to a computer. That computer automatically uses the second non-secure network to contact the person back to verify the transaction. The call-back mechanism employs a method to authenticate the identity or authority of the person initiating the transaction. No single wire-tapping or network snooping device sees the entire transaction. No single database contains the entire set of information.

Abstract: A satellite-based digital broadcast system is used to provide real-time news, entertainment and informational programs to aircraft passengers in flight. Transmissions from the satellite occur on a time division multiplex (TDM) downlink with different broadcast programs being transmitted on different TDM channels. A broadcast receiver is carried on board the aircraft, and includes a demultiplexer for demultiplexing the TDM channels to reproduce the original broadcast programs. The broadcast receiver may be adapted to receive and reproduce both audio and video broadcasts, as well as to provide other types of information delivery services. Encryption of the broadcast programs may be used to restrict their use to a specific aircraft or airline company.

Abstract: According to a cryptographic communication system which can safely perform cipher conversion processing when cryptographic communication is performed between terminals using different cipher types, when a terminal 10A-1 connected to a LAN-A using a cryptographic algorithm C1 transmits data to a terminal 10B-1 connected to a LAN-B using a cryptographic algorithm C2, the terminal 10A-1 generates two meaningless data items from the data to be transmitted, decrypts the two generated data items according to the cryptographic algorithm C1, and then transmits the decrypted data to two cryptographic protocol conversion servers and for dividing the data into two data items. Each of the cryptographic protocol conversion servers decrypts each transmitted data item, the re-encrypts the decrypted data according to the cryptographic algorithm C2, and then transmits the data to the terminal 10B-1.

Abstract: A state synchronized cipher text scrambler is disclosed. The state synchronized cipher text scrambler enables multiple data streams to be scrambled in parallel in such a way that the data streams are uncorrelated with respect to each other and there is a large fixed delay relationship between the scrambler bits over the multiple streams. This enables a receiver to correctly identify the ordering of the multiple data streams with respect to each other automatically, correct for any polarity or wire-swap misconnections and align the received multiple data streams despite differential delays between the data streams.

Abstract: The invention provides a digital data shuffling/de-shuffling system so that information data is not understood or deciphered by unauthorized third party. Included are a system for generating plural bits of digital data to be transmitted, a circuit network 7 having a plurality of input terminals #1 through #8 and output terminals #11 through #18 equal to the number of bits to be transmitted and a plurality of switching circuits S for selectively cross connecting or non-cross connecting between two lines out of a plurality of transmission lines a.sub.1 through a.sub.8 interconnecting the corresponding input and output terminals, and a control circuit P for controlling the plurality of switching circuits S. The control circuit P is controlled to shuffle the data applied to the input terminals #1 through #8 for providing the shuffled output from the output terminals #11 through #18.

Abstract: A method and apparatus for substantially reducing electromagnetic radiation from a backplane used to interconnect multiple communication modules. Data signals to be transmitted onto the backplane are first scrambled using a pseudorandom code sequence, to reduce energy peaks in the radiation spectrum and to spread energy over a wider bandwidth. Signals received from the backplane are descrambled using an identical pseudorandom code sequence. Data rate synchronization is provided by recovery of a data clock signal from the received scrambled signals, and data frame synchronization is provided by transmitting data frame headers as non-scrambled data. At a receiver module, the frame headers are detected and used to reset the descrambling operation.

Abstract: The invention relates to a device (1) for processing data packets, comprising identification means (14) for identifying a data packet, processing means (11, 12) for cryptographically processing the data packet, and memory means (13) for storing information relating to the processing, in which device the processing means comprise at least a first (11) and a second (12) processing unit. Control means (14) are provided to assign, on the basis of the identification of a data packet, said data packet to one of the processing units and to process said data packet with the aid of information related to said data packet. Preferably, at least one processing unit (11; 12) is designed to encrypt or decrypt data packets, and the information relating to the processing comprises a key and a status of a processing procedure.

Abstract: A software-efficient pseudorandom function maps an index and an encryption key to a pseudorandom bit string useful for constructing a stream cipher. The method begins by preprocessing the encryption key into a table of pseudorandom values. The index and a set of values from the table is then used to generate a set of initial values for the registers. At least some of the register values are modified in part by taking a current value of a register and replacing the current value with a function of the current value and a value retrieved from the table, the latter value being determined by the values in one or more other registers. After modifying the register values in this fashion, the values are masked using other values from the table and the results then concatenated into the pseudorandom bit string. The modification step is repeated and a new masked function of the register values is then concatenated into the pseudorandom bit string.

Abstract: The present invention concerns a method for the manipulation-proof separation of message streams, which are transmitted in the subscriber loop (3) of a communication network via a medium (30) that is common to several subscribers, where first measures (22, 43) are taken to separate the message streams for transmission via the common medium, which are identical for all message streams, and for connections between at least one subscriber (4) connected to the communication network via the common medium, and another subscriber, supplementary measures (111, 112, . . . , 11n; 42) are taken from end to end, which were agreed between these subscribers for these connections, as well as a suitable system and a suitable subscriber facility.

Abstract: An analog optical encryption system based on phase scrambling of two-dimensional optical images and holographic transformation for achieving large encryption keys and high encryption speed. An enciphering interface uses a spatial light modulator for converting a digital data stream into a two dimensional optical image. The optical image is further transformed into a hologram with a random phase distribution. The hologram is converted into digital form for transmission over a shared information channel. A respective deciphering interface at a receiver reverses the encrypting process by using a phase conjugate reconstruction of the phase scrambled hologram.

Abstract: An apparatus and method for voice privacy for cellular phones includes generic connection points to make it universal for most cellular phones. The connection points include the speaker and microphone and the microphone input and speaker output of the cellular phone. A scrambling or encryption circuit or process is used to secure the audio before it is transmitted over the network, and the unsecured audio once received. Side-tone added by the cellular phone and network echo of the scrambled audio to be transmitted is removed by, for example, adaptive echo cancellation, and unscrambled side-tone is presented to the speaker. The apparatus can be implemented in a digital signal processor.

Abstract: A digitized real voice signal is converted via complex filtering into a complex signal that is subjected to sampling rate reduction, the bandwidth of the respective complex filter corresponding to the sampling rate. The complex signal is phase-modulated by means of a code signal generated by a random-number generator and additively combined with a pilot signal (likewise phase-modulated in a random distribution) to form an encrypted useful signal for transmission. The useful signal is sequentially transmitted together with a preamble for synchronization and signal equalization at the receiver end. At the receiver end, clock synchronization is forced for a phase-modulated pilot signal produced at the receiver end and equalizer coefficients for an equalizer at the receiver end are calculated from the digitized received signal after complex filtering and corresponding sampling rate reduction, during a preamble recognition phase, at which point the phase of the useful signal decryption is initialized.

Abstract: Individual information signals encoded with a common block error-correction code are assigned a unique scrambling mask, or signature sequence, taken from a set of scrambling masks having selected correlation properties. The set of scrambling masks is selected such that the correlation between the modulo-2 sum of two masks with any codeword in the block code is a constant magnitude, independent of the mask set and the individual masks being compared. In one embodiment, when any two masks are summed using modulo-2 arithmetic, the Walsh transformation of that sum results in a maximally flat Walsh spectrum. For cellular radio telephone systems using subtractive CDMA demodulation techniques, a two-tier ciphering system ensures security at the cellular system level by using a pseudorandomly generated code key to select one of the scrambling masks common to all of the mobile stations in a particular cell.

Abstract: Individual information signals encoded with a common block error-correction code are assigned a unique scrambling mask, or signature sequence, taken from a set of scrambling masks having selected correlation properties. The set of scrambling masks is selected such that the correlation between the modulo-2 sum of two masks with any codeword in the block code is a constant magnitude, independent of the mask set and the individual masks being compared. In one embodiment, when any two masks are summed using modulo-2 arithmetic, the Walsh transformation of that sum results in a maximally flat Walsh spectrum. For cellular radio telephone systems using subtractive CDMA demodulation techniques, a two-tier ciphering system ensures security at the cellular system level by using a pseudorandomly generated code key to select one of the scrambling masks common to all of the mobile stations in a particular cell.

Abstract: A software-efficient pseudorandom function maps an index and an encryption key to a pseudorandom bit string useful for constructing a stream cipher. The method begins by preprocessing the encryption key into a table of pseudorandom values. The index and a set of values from the table is then used to generate a set of initial values for the registers. At least some of the register values are modified in part by taking a current value of a register and replacing the current value with a function of the current value and a value retrieved from the table, the latter value being determined by the values in one or more other registers. After modifying the register values in this fashion, the values are masked using other values from the table and the results then concatenated into the pseudorandom bit string. The modification step is repeated and a new masked function of the register values is then concatenated into the pseudorandom bit string.

Abstract: A system for encoding and decoding an audio transmission signal comprises: (a) an encoder with a frequency-varying means to vary the carrier frequency of the audio signal according to an encryption algorithm; (b) a transmitter; (c) a receiver; and (d) a decoder with a multi-plexing filter for separating segments of the audio signal with identical carrier frequencies, and a demodulator corresponding to each carrier signal frequency. The separated segments of the audio signal are switched to the corresponding demodulators according to a decryption algorithm.

Abstract: In the transmission of information which require secrecy, such as voice and data, serial bit streams having bit rates of more than 100 Mbit can occur, particularly given digital signal hierarchies according to the CCITT recommendations. In order to be able to utilize integrated circuits constructed in CMOS technology having low power consumption for the realization of cryptographic equipment for bit streams having such a high bit rate, it has already been proposed that a plurality of subcoders or, respectively, subdecoders be utilized upon employing multiplexing techniques. Given the utilization of subcoders and subdecoders having the same crypto-codes, a special synchronization between a demultiplexer and a multiplexer at the transmitting side, on the one hand, and at the receiving side, on the other hand, can be foregone given employment of individual synchronization of the subcoders and, respectively, subdecoders assigned to one another at the transmitting side and at the receiving side.

Abstract: A signal of bandwidth F.sub.max is unambiguously transmitted over a datalink having a bandwidth less than F.sub.max by subdividing the signal into a plurality of subspectrums and bandshifting the subspectrums greater than the datalink bandwidth to baseband. Each bandshifted subspectrum is uniquely encoded using a different pilot tone which can be detected by the receiver to decode the receive signal and unambiguously recover the narrowband spectrum components.

Abstract: A composite spread spectrum signal including modulator and demodulator therefor is disclosed. The composite signal having a multi-dimensional signal space, comprising a pulse position modulation dimension generated by varying starting positions of cyclically repeated chipping sequences, a frequency shift key dimension generated by varying a carrier frequency between a plurality of frequencies, code shift keyed dimensions generated by selecting the chipping sequences from among a plurality of orthogonal sequences, and amplitude shift key dimensions generated by selecting amplitudes of each subcarrier for each message bundle. This signal may further comprise a phase shift key dimension generated by assigning a phase relationship of the orthogonal subcarriers.

Abstract: A software-efficient pseudorandom function maps an index and an encryption key to a pseudorandom bit string useful for constructing a stream cipher. The method begins by preprocessing the encryption key into a table of pseudorandom values. The index and a set of values from the table is then used to generate a set of initial values for the registers. At least some of the register values are modified in part by taking a current value of a register and replacing the current value with a function of the current value and a value retrieved from the table, the latter value being determined by the values in one or more other registers. After modifying the register values in this fashion, the values are masked using other values from the table and the results then concatenated into the pseudorandom bit string. The modification step is repeated and a new masked function of the register values is then concatenated into the pseudorandom bit string.

Abstract: A system for secure communications between first and second locations where he first location measures the location of the second location. The first location then codes that measured location along with a random reply channel code for communications from the second location to the first location. The first location then transmits the two codes to the second location which decodes the two signals. The second location then measures it's own location and compares it with the received location. The newly measured location is coded and transmitted to the first station on the randomly selected reply channel.

Abstract: A communication system in accordance with the invention employs a broadcast signal for synchronization of the transmitters and receivers in the system without use of a special base transmitter for synchronizing signal transmissions. Each transmitter having a pre-assigned time slot counts from a synchronizing index which is inherent in or added to the broadcast signal to determine when to transmit. The receiver of receivers similarly count from the synchronizing index to determine when to look for specific time slice transmissions.

Abstract: An improved DES unit internally checks whether the DES algorithm is being performed without error. A standard DES algorithm performs an initial permutation of input data and then multiple rounds or iterations of the following: expanding part of a result of the initial permutation for the first iteration and a result of the previous iteration for the subsequent iterations, exclusive ORing a result of the expansion with key bits, performing a selection function on a result of the exclusive ORing, permuting a result of the selection function, and exclusive ORing a result of the permuting. In the improved DES unit, data check bits that correspond to the input data which has been expanded are exclusive NORed with key check bits that correspond to the key, and a result of the exclusive NORing is checked against a result of the exclusive ORing to identify any errors in the operation of the basic DES unit. Also, a check selection function is performed on the result of the exclusive ORing.

Abstract: The present invention provides a modulation/ demodulation circuit and a communication system utilizing the modulation/demodulation circuit. The modulation/ demodulation circuit can be operated in either of a modulation/demodulation mode wherein an input signal is frequency inverted and scrambled or descrambled and a through mode wherein the input signal is directly outputted therefrom without being subject to any processing. In a private communication system, two such modulation/ demodulation circuits are used as a scrambler in the transmission-side and as a descrambler in the reception-side. In order to prevent the low band characteristic of the reception-side output in the through mode from being different from that of the modulation/demodulation mode, the modulation/demodulation circuit may include a high pass filter. The high pass filter a low band cut-off characteristic reciprocal to a low pass filter for removing the upper side band from the output of a double balanced mixer.

Abstract: A security node disposed in the telecommunications network connecting calling and called parties transforms information (which can be voice, data, facsimile, video and other types of calls or messages) encrypted in a first format to (a) encrypted information in a different format or to (b) non-encrypted information, and vice-versa. The node is accessible from any location connected to the network. By routing calls or messages originated by the calling party and destined for the called party via the security node, and providing appropriate control signals to the node, the information may be encrypted only over a portion of the transmission path between the parties, and clear over the remainder of the transmission path. Alternatively, the information may be encrypted in different portions of the path using different encryption algorithms.

Abstract: Parallel working additive scramblers produce a predetermined pseudorandom sequence of length L in a word generator, which consists of an N-stage shift register. To obtain more than N parallel located pseudorandom sequences, the word generator is connected to a network in which, in addition to the pseudorandom sequences created by modulo-2 addition, other pseudorandom sequences are created with a different phase relation. Performing the linkage operations limits the maximum bit rate sequence that can be transmitted. The entire pseudorandom sequence is stored in a memory (S). The desired pseudorandom sequence is produced in a circular storage (RS) by means of shifting operations. The circular storage (RS) is in the form of a feedback shift register (SR) and is used as the memory (S), in which each of the outputs is connected to an input of an EXOR-gate, in which a pseudorandom sequence is modulo-2 added with a partial stream of a parallelized serial data stream.

Abstract: A method for transparently coupling an encrypted two-way RF communication unit (100) with an encrypted landline communication unit (104). An RF message comprised of a plurality of data frames (401,402, 403) is transmitted from the RF communication unit (100), wherein a plurality of the data frames include encrypted voice information (403). Some bits from the data frames (501,502) are selectively removed, without removing the encrypted voice information (503), to form reduced bit data frames, and the reduced bit data frames are transmitted via the landline to the landline communication unit (104).

Abstract: Secure teleconferencing between three or more parties is achieved by receiving encrypted information streams from each of the parties to the conference. The encrypted information streams are received in decryption/re-encryption units co-located with a conference bridge established in a telecommunication switching system in a public switched telephone network central office. The decryption/re-encryption units decrypt the information streams and then re-encrypt those information streams in accordance with a common conference encryption algorithm. The re-encryption processes for the information streams are synchronized so that the re-encryption circuitry for all information streams are in the same cryprostate at all times during the re-encryption procedure. The decryption/re-encryption units are located in secure surroundings to protect the unencrypted information streams present in those units.

Abstract: A video encryption/decryption system in which lines of video information are stored in digitised form in a block of RAM memory, and are typically shuffled in groups of 32 lines by pivot reading information corresponding to 32 lines from the memory in a first predetermined order, which may for example be sequential order, and writing new input line information into the corresponding locations, and then reading from, and writing to, the memory in a second different order which may be random or pseudo-random, and subsequently repeating these two read/write operations alternately. This enables the line shuffling process to be achieved with a reduced memory requirement, compared with known methods.

Abstract: A re-authentication procedure between the modems of a public switched telephone network (PSTN) data connection, which is between a computer facility and a user, provides a secure method for protecting the computer facility against an active wire tap, or spoofing, by an intruder. In particular, the user's modem and the computer's modem perform a re-authentication procedure throughout the duration of the data connection. This re-authentication procedure is transparently performed on a side channel of the data connection. This side channel can either be an in-band channel or an out-of-band channel. The re-authentication procedure comprises an exchange of encrypted information between the two modems. If one of the modems detects the presence of an active wire tap, that modem simply interrupts the data connection.

Abstract: An encryption/decryption device, system and method for providing secure communication over a communication channel. The encryption device includes a radio interface unit connected to a conventional radio, wherein the interface unit selectively couples a codec, signal processor and modem to the transmit and receive path during secure operation. The codec digitally encodes non-secure analog signals and places them in pulse code modulated format. The signal processor then compresses the pulse code modulated signals into voice coded and then digitally encrypted NRZ signals which are then input into the conventional radio for modulating a carrier frequency on an occupied bandwidth approved for 15 KHz to 25 KHz, or as little as 11.4 KHz, spaced channels. The modem can input the digitally encrypted signals using modified frequency modulation to place the modified digitally encrypted signals substantially within the voice passband of 300 Hz to 3200 Hz.

Abstract: On the transmitter side, data to be transmitted are converted into a plurality of parallel data sets by a serial-parallel converter 101 and spread spectrum modulation is effected by means of PN code generators 105 and selectors 102. Each of the modulated outputs is delayed by a delaying circuit 103 with reference to a sounder channel and the phase thereof. The output thus delayed and the output of the sounder channel are added by an adder 104 to be multiplexed and transmitted.On the receiver side, correlation between a received signal and a reference signal is formed by a correlator 201 to obtain a correlation pulse from the correlation output thus obtained. Data demodulation is effected by means of a sounder detecting circuit 209, a sampling pulse generating circuit 210 and an information detecting circuit 211, starting from this correlation pulse.According to the structure described above, in SS communication, data demodulation can be effected with a high efficiency by using a single correlator.

Abstract: Of the type formed by a pseudorandom code generator and a block that performs the synchronizing and the scrambling in parallel which, in addition to the initialization signal, receives as inputs the set of parallel input data and the codes generated by the code generator, and produces the scrambled parallel data at the outputs; the modulo-2 adders used in the feedback loops of the pseudorandom code generator have only two inputs, and the outputs of the code generator in the parallel working time slots tp and tp+1 are related through the expression:C.sub.tp+1 =T.sup.n (nxn).C.sub.tpsimplifying the result accordingly.

Abstract: A data communication system adaptable to a ciphered data communication includes a data transmission line (3) for transmitting ciphered or non-ciphered data between a data transmitting device and a data receiving device 11, a data transmitting device (1) for transmitting data, a data receiving device (5) for receiving data transmitted through the data transmitting device, a data ciphering apparatus (2) on the side of the data transmitting device, and a data deciphering apparatus (4) on the side of the data receiving device. The data ciphering apparatus including switching device (2A), line condition detector device (2B) control code monitor, scrambling device (2E), and drive control (2D). The line condition detector device, the control code monitor, and the scrambling device supply the transmission line through the switching device with ciphered data of the data from the data transmitting device.

Abstract: A remotely retunable receiver for use in a satellite video programming distribution system includes the capability to retune groups of subscribers to different satellite feeds during a blackout of a video programming event. To achieve flexible control over program blackouts, a receiver retune command message is selectively sent to desired groups of descramblers at CATV satellite downlinks. The retune command message identifies an alternate satellite feed and a time for which the satellite receiver is to tune to the alternate satellite feed. The receiver stores the retune command, and at the appropriate time retunes the satellite receiver to the identified alternate feed. By command messages received on the alternate feed, the group of blacked out satellite receivers are returned to the original programming channel at the end of the blacked out event.

Abstract: A repeater diversity spread spectrum communication system provides substantially fade free communications between a transmitter (1) and a receiver (7). A transmitted signal is relayed through a plurality of linear communications repeaters (3-6) that produce copies of the transmitted signal, the copies each arriving through an independently fading signal path. The transmitter and/or the receiver may be mounted upon a mobile platform, and the plurality of repeaters may be terrestrial, or may be provided in satellites in low earth orbit or in geosynchronous earth orbit. The receiver processes the received signal copies to equalize them to one another in delay, frequency, and phase, and then combines the multiple received and equalized signal copies to produce a composite signal having a greatly reduced fading depth.