Abstract: The present invention relates to a system for calibrating translation equons of a gyro navigator of a submarine. A value of velocity and a value of position of the submarine are produced by using values of acceleration sensed by accelerometers in the navigation gyro. The value of velocity and position are produced with the aid of the translation equations. This value of velocity and value of position are compared with a value of velocity and a value position as produced by a more accurate and independent source. A comparison is made with the aid of Kalman filter. Any difference obtained during a comparison is used in order to calibrate the translation equations of the gyro navigator.

Abstract: A digital message M is transformed by means of an operation to modulo-N exponentiate M by a number e all these numbers being large-length integers, having n bits, which uses a sequence of two successive operations, the first in the form of:B.sub.i =a.sub.i.X+T.2.sup.mwhere B.sub.i and X are calculation variables, where a.sub.i is an extract of m bits of a second calculation variable A whose value results from a previous operation, which extract is taken in the decreasing order of weight of A, of rank i, and where T is a summing variable used for the calculation of the variable A, and the second operation consists of reducing the length of the variable B.sub.i. A modulo-N quasi-reduction is used because it is approximative (to the nearest small multiple of N), and may be applied systematically and without a sign test during a given number of successive operations which are chosen, after which a supplementary and systematic reduction is performed according to the same method.

Abstract: A countermeasure to a partial-band follower jammer for frequency hopping spread spectrum communication systems employs an M-ary orthogonal frequency shift keyed (FSK) signaling system having q frequency channels available for hopping. During each signaling interval, the transmitter and receiver operate in either a conventional or unconventional mode. The conventional mode is selected by the transmitter and the receiver with a pseudorandom probability p.sub.c. In this mode, the transmitter transmits one of r tones within the corresponding hop (i.e., within one of q channels), and log.sub.2 r information bits are conveyed, while the receiver comprises a dehopper followed by noncoherent matched filters. The unconventional mode is selected with probability 1-p.sub.c. In this mode, the transmitter randomly chooses one of the r tones and transmits it in one of r channels within each hop, where the r channels are selected pseudorandomly. In the unconventional mode, log.sub.

Abstract: A digital equalizer and equalization method for a spread spectrum communication link that has a dispersive channel and other systems that process signals having a sufficient degree of redundancy in time and/or phase. No training signal is required, except for an initialization bit sequence. The receiver incorporating the equalizer uses correlation over a bit time between a received signal, that includes data modulation, and a locally generated spreading signal that does not. The output of the correlator is a set of complex digital samples (I and Q-channel) taken at the spreading sequence bit rate. In the absence of multipath dispersion, there is perfect cross-correlation function, and hence only one large sample per transmitted data symbol. With multipath dispersion, the received energy is spread over two or more samples of the correlation.

Abstract: Device A in a public key cryptographic network will be constrained to continue to faithfully practice a security policy dictated by a network certification center, long after device A's public key PUMa has been certified. If device A alters its operations from the limits encoded in its configuration vector, for example by loading a new configuration vector, device A will be denied participation in the network. To accomplish this enforcement of the network security policy dictated by the certification center, it is necessary for the certification center to verify at the time device A requests certification of its public key PUMa, that device A is configured with the currently authorized configuration vector. Device A is required to transmit to the certification center a copy of device A's current configuration vector, in an audit record. the certification center then compares device A's copy of the configuration vector with the authorized configuration vector for device A stored at the certification center.

Abstract: A credit card system uses an encryption algorithm to generate a first encoded text from the card number and a password supplied by the user. The card user is verified by comparison of the first encoded text with an encoded text recorded on the card. When the transaction is completed, the merchant generates a receipt containing a first verification code generated from the date and time of the transaction, the merchant's identification number, the password, and the card number. To receive payment, the merchant presents the receipt to the credit card center. The credit card center generates a second verification code from the card number, the password which is retrieved from the central database, the merchant number, and the time and date of the transaction. If the two verification codes match, the merchant is credited with the amount of the transaction.

Abstract: The cryptographic system is comprised of two stations A and B in which a respective string S.sub.A and S.sub.B of digits is stored. In station A an error-control information string C is generated from string S.sub.A and transmitted to station B over an error-free public channel CH1. In station B a particular string D and a decision bit F are generated. String D maximizes a predetermined reliability function of a string combination (S.sub.B, C, D). Decision bit F is assigned the value 1 if and only if a maximum value taken on by the reliability function is greater than a predetermined threshold. Decision bit F is transmitted to station A over an error-free public channel CH2. In both stations A and B, the respective strings S.sub.A and S.sub.B are tagged as accepted when said decision bit F has the value 1. The above sequence is repeated, resulting in a plurality of tagged strings which are concatenated at stations A and B to result in a random cipher key shared by the stations A and B.

Abstract: A spread spectrum transmitter uses simultaneous pseudorandom shifts of the transmitted carrier phase and receive local oscillator phases by 90 or 45 degrees and/or pseudorandom time shifts of the transmitted and receiver chip timing by half a chip duration to limit the coherent integration of carrier and chip rate detectors at an intercept receiver attempting to detect the transmissions. Direct sequence spread spectrum signals are intercepted and identified using an intercept receiver by recovering a spectral line corresponding to their carrier frequency or to their direct pseudo-noise chip rate. The conventional use of a phase shift with a fixed carrier frequency and/or a chip time shift with a fixed chip rate simplifies the design of the intercept receiver because the receiver is optimized to a single carrier frequency and chip rate.

Abstract: A packet data transmission system is used to link a number of remote hand-held data-gathering units such as bar code readers to a central computer which maintains a database management system. Data packets are sent from the remote units by an RF link to intermediate base stations, then sent by the base stations to the central computer by a serial link. Direct sequence spread spectrum modulation is used for the RF link. The remote hand-held units initiate an exchange using RF transmission to and from the base stations, receiving only during a rigid time window following a transmission from the remote unit. The base stations cannot initiate communication to the remote units, but instead send data to the remote units only as part of the exchange.

Abstract: A variable pulse rate circuit for correlating a locally generated code with code that is being transmitted by a space vehicle. A computer means is used for providing a binary word to a latch. The binary word in the latch is used in turn by a delay line, to control the amount of delay that is presented to pulses. The pulses are emitted by a pulse generator having a fixed rate reference. The pulse rate, of pulses being emitted by of the delay line, is varied from the reference pulse rate. This variation is the result of computer means that rapidly changes the amount of delay of the delay line. The pulse rate and the pulse phase are varied in order to cause a locally generated code to become phase aligned with the code received from the space vehicle. The space vehicle is tracked using the variable pulse rate circuit.

Abstract: A modem security communication system for providing access to a computer system having a host computer and a central access controller located at a host location, and user terminals with transponders at a plurality of remote locations. The modem security communication system also includes at least one modem at each of the host and remote locations for interaction with the host computer and transponder, respectively. The transponder is arranged to receive a spoken word from a computer user whereby an analog signal is converted to a digital signal, compressed, encrypted, and transmitted to the host location where it is decrypted and compared with a stored signal on a voiced template corresponding to an identified user's voice. The system further provides for initial communication between the transponder and the host controller to sustain the communication link. This communication may also be encrypted for security.

Abstract: The invention provides an improved communication terminal system which basically works only in an on-line state, that is, when it is connected with a host computer; but, which is also workable for a pre-determined time period even in an off-line state. The communication terminal system includes a terminal unit, measuring means for counting working frequency or time of the terminal unit, and control means for detecting disconnection from the host computer and controlling the terminal unit. The control means activates the counting means when it detects disconnection of the communication lines. The control means then disables the terminal unit when it detects that working frequency or time of the terminal unit amounts to a value previously set on the measuring means.

Abstract: A descrambler for descrambling scrambled information signals through use of a predetermined decryption key. The processing means are adapted for processing data in accordance with a number of different data processing routines to descramble said scrambled information signals, including a routine for descrambling said scrambled information signals that utilizes said predetermined decryption key, and a routine for generating said predetermined decryption key.

Abstract: Substractive CDMA demodulation optimally decodes a coded information signal embedded in may other overlapping signals making up a received, composite signal. A radio receiver correlates a unique code corresponding to the desired signal to be decoded with the composite signal. Moreover, after each information signal is successfully decoded, it is recoded and removed from the composite signal. As a result, subsequent correlations are performed with greater accuracy. Substractive CDMA demodulation is enhanced by decoding the composite signal in the order of strongest to weakest signal strength. Interference caused by the presence of the strongest information signal and the composite signal during the decoding of weaker signals is removed. The individual information signals are assigned a unique block error correction code with is correlated with the composite signal using Fast Walsh transforms. Correlated signals are recoded using inverted Fast Walsh transforms and removed from the composite signal.

Abstract: A security module for a radio telephone prevents a KEY code stored in a non-volatile memory from being read out for illicit use. The security module deletes the KEY code stored in the memory when accessed from the outside. Hence, although a KEY code can be written to the memory or the operation of the memory can be tested from the outside, the KEY code is prevented from being read out by an unauthorized person.

Abstract: This method of key distribution locates (401,501) an individual communication unit (107) within an encrypted communication system with over-the-channel rekeying and then rekeys (415, 515) the unit. The method uses a key management controller (101) to manage and distribute keys (1541) and handle acknowledgments that are either immediate or delayed from receipt of the rekeying message.

Abstract: An apparatus and a method for the identification and encrypting/decrypting of messages permits converting an input message provided as characters, in character-by-character fashion and depending on preceding characters, to form an output message. An address branching network is employed for encrypting/decrypting. The address branching network includes selectable branches that are carriers of encrypting/decrypting characteristics. The selection of such branches is done in a step-by-step selection run through the branching network to convert any specific input message of optional length character-by-character into a specific selection path through the branching network. The output message is formed on the basis of the encrypting/decrypting characteristics from the branches selected on said selection path.

Abstract: Hardware complexity of transmitting and receiving equipment in a CDMA (Code Division Multple Access) cellular radio transmission system, embodying the principles of the invention, is reduced by the use of frequency modulation (FM) techniques to achieve spectral spreading in combination with signal modulation.The spectral spreading technique of a CDMA cellular radio telephone communications system is generalized by extending the range of values allotted to the spreading waveform code signal to include complex numbers of unity magnitude. This permits the addition of a baseband version of the information signal and spreadying waveforms instead of the conventional multiplication of the two signals in existing DSSS (Direct Sequence Spread Spectrum) communications sytems. The resultant summed signal is used to control a VCO (Voltage Controlled Oscillator) to produce a frequency modulated spread signal to be transmitted.

Abstract: A device for storing user data and a value representative of the time of storage is disclosed, which includes physically separating portions of an encryption key, combining a time stamp with user data, and using the restored encryption key to encrypt and decrypt the stamped user data.

Abstract: An improved security system is disclosed which uses an IC card to enhance the security functions involving component authentication, user verification, user authorization and access control, protection of message secrecy and integrity, management of cryptographic keys, and auditability. Both the security method and the apparatus for embodying these functions across a total system or network using a common cryptographic architecture are disclosed. Authorization to perform these functions in the various security component device nodes in the network can be distributed to the various nodes at which they will be executed in order to personalize the use of the components.