Abstract: A system for facilitating secure network communications includes a security computer system and corresponding software. The security system is utilized in conjunction with a voice browser residing on a server system. A user accesses the network by placing a call to the voice browser system. The voice browser includes a software module that creates a secure connection to the security system. The user provides an identification to the voice browser system that is transferred to and verified by the security system. Once the identification is verified, the user is prompted by the voice browser system to speak a phrase for voice verification. The verification speech signals are transferred from the voice browser system to the security system to verify those speech signals against speech signals of a particular authorized user associated with the identification and stored in a database. When the user is verified, the security system retrieves a user private key and certificate from the database.

Abstract: A method is disclosed for establishing trusted communications with associations for communications between users on an Internet Protocol based computer network. The method entails the first user's SNIU determining the Internet Protocol (IP) address of a second user's SNIU on the computer network through the use of custom and ICMP Echo Request and Reply messages. The user's SNIUs exchange security related information needed to complete the establishment of a trusted association. The trusted association is maintained during all communications between the first user and the second user.

Abstract: A method is disclosed for establishing trusted communications with associations for communications between users on an Internet Protocol based computer network. The method entails the first user determining the Internet Protocol (IP) address of a second user on the computer network through the use of Address Resolution Protocol (ARP) and Reverse Address Resolution Protocol (RARP). The first user then determining the accessability of the second user on the computer network. The users exchange security related information needed to complete the establishment of a trusted association. The trusted association is maintained during all communications between the first user and the second user.

Abstract: A method is disclosed for mixed enclave operation of a computer network with users employing a multi-level network security interface and users without any network security interface. Either the network security user selects or the network security interface automatically selects whether communications are permissible with other unsecured users. Where a mixed enclave operation is selected, the network security user identifies when communications are being undertaken with another secured user or a non-secured user. Communications with a non-secured user at a lower security level entail securing the data residing with the secured user from transmission back to the non-secured user.

Abstract: A multi-level security device is disclosed for providing security between a user and at least one computer network, wherein the user is selected from the group consisting of a host computer and at least a second network. A secure network interface Unit (SNIU) that operates at a user layer communications protocol, which communicates with other like SNIU devices by establishing an association at a session layer of a communication stack in order to create a global security perimeter for end-to-end communications. The SNIU includes a host/network interface for receiving messages sent between the user and the at least one network, which is operative to convert the received messages to and from a format utilized by the at least one network. A message parser for determining whether the association already exists with another SNIU device. A session manager coupled to the interface for identifying and verifying the user requesting access to the network.

Abstract: A method is disclosed for limited write downs of data from higher security classification users to lower security classification users across computer networks, while preserving the security of classified data at the higher security classification user from covert transmission via acknowledgment messages from the higher user to the lower user. The intended acknowledgment message is released to the lower user when it matches the user content of a predicted acknowledgment message. In TCP/IP interface applications, the acknowledgment messages are IP based data transfer protocols acknowledging the transfer of data from the lower side to the higher side. With IP datagram transfers, deterministic portions are predicted and non-deterministic portions are identified. Where the number of non-deterministic bits exceed a predetermined rate, the acknowledgment message is discarded.

Abstract: A real-time speech processing development system has a control subsystem (CS) and a recognition subsystem (RS) interconnected by a CS/RS interface. The control subsystem includes a control processor, an operator interface, a user interface, and a control program module for loading any one of a plurality of control programs which employ speech recognition processes. The recognition system RS includes a master processor, speech signal processor, and template matching processors all interconnected on a common bus which communicates with the control subsystem through the mediation of the CS/RS interface. The two-part configuration allows the control subsystem to be accessed by the operator for non-real-time system functions, and the recognition subsystem to be accessed by the user for real-time speech processing functions.

Abstract: An apparatus operates to identify the speech signal of an unknown speaker as one of a finite number of speakers. Each speaker is modeled and recognized with any example of their speech. The input to the system is analog speech and the output is a list of scores that measure how similar the input speaker is to each of the speakers whose models are stored in the system. The system includes front end processing means which is responsive to the speech signal to provide digitized samples of the speech signal at an output which are stored in a memory. The stored digitized samples are then retrieved and divided into frames. The frames are processed to provide a series of speech parameters indicative of the nature of the speech content in each of the frames.

Abstract: A method and apparatus for recognizing an unknown speaker from a plurality of speaker candidates. Portions of speech from the speaker candidates and from the unknown speaker are sampled and digitized. The digitized samples are converted into frames of speech, each frame representing a point in an LPC-12 multi-dimensional speech space. Using a character covering algorithm, a set of frames of speech is selected, called characters, from the frames of speech of all speaker candidates. The speaker candidates' portions of speech are divided into smaller portions called segments. A smaller plurality of model characters for each speaker candidate is selected from the character set. For each set of model characters the distance from each speaker candidate's frame of speech to the closest character in the model set is determined and stored in a model histogram. When a model histogram is completed for a segment a distance D is found whereby at least a majority of frames have distances greater D.

Abstract: A real-time amplitude histogram shaper transforms an input analog signal with a corresponding input amplitude histogram to an output signal with a specified output histogram. The histogram shaper comprises a histogram estimator, which estimates the amplitude histogram of an input analog signal. A calculator, whose input is connected to the output of the estimator, computes the transfer function required to transform the input signal to an output signal with the desired amplitude histogram. A controller, whose input is connected to the output of the calculator, generates control signals. A transfer function generator, whose input is connected to the output of the control signal generator, modifies its input signals by a ratio P.sub.out /P.sub.in. The gain P.sub.out /P.sub.in is a function of P.sub.in, that is, P.sub.out /P.sub.in =g(P.sub.in).P.sub.out is the magnitude of the output parameter and P.sub.in is the magnitude of the input parameter, the output signal thereby having the desired amplitude histogram.

Abstract: An image-compression system, wherein the image consists of a planar array of data points having various brightness levels, comprises a transmitter and a receiver. The transmitter comprises an analog-digital converter, for converting input analog data into digital data. The cosine transform is taken of the incoming digital data to transform the data representing various brightness levels into the frequency domain. The various frequency data points are differentially pulse code modulated, thereby removing line-to-line redundancy, the output data being in parallel form. Timing circuitry is provided for controlling the timing of the various circuits. Circuitry is provided in a receiver for the modulating or decoding of the output signal of the transmitter.

Abstract: A charge-coupled device (CCD) multiplying digital-to-analog converter mullies a bipolar analog signal, representing as a charge, by a digital word, and produces a four-quadrant analog product, also represented as a charge. An analog signal S is added to or subtracted from a bias, resulting in signals S+B and -S+B, which are converted into corresponding positive charges, Q.sub.S +Q.sub.B and -Q.sub.S +Q.sub.B, which are transferred into potential wells at X.sub.i and Y.sub.i, respectively. A digital word may be represented as b.sub.1 b.sub.2 b.sub.3 . . .b.sub.N, where N is the word length. The CCD converter comprises N parallel devices, each of which performs the function of multiplying the signal S by either 0 or 1/2.sup.i. A gate between X.sub.i and Y.sub.i is controlled by the binary bit b.sub.i. Equilibration occurs or does not occur depending on whether b.sub.i equals 0= or 1. The charges left in X.sub.i and Y.sub.

Abstract: An apparatus is capable of recovering signals from N sites, N.gtoreq.2, distributed along a single coaxial cable. This multiplexing technique allows the separation of signals from many transducers on one line. Time domain reflectometry (TDR) is used, with variable resistive elements distributed along the cable. TDR is used to detect discontinuities in the impedance of the cable as well as their specific location along the cable. The magnitude of these discontinuities is modulated by an impedance that is proportional to the applied signal. An excellent way of obtaining this kind of variable impendance along the line is to bias a field effect transistor (FET) so that it functions as a variable resistor. For a large number of signals to be multiplexed onto a coaxial cable, an FET is placed at each of the N signal sources. The coaxial cable has a characteristic impedance of Z.sub.o and the FET's are evenly spaced at a distance l.