Showing papers by "National Security Agency published in 2000"

Kronos: a scalable group re-keying approach for secure multicast

Abstract: The authors describe a novel approach to scalable group re-keying for secure multicast. Our approach, which we call Kronos, is based upon the idea of periodic group re-keying. We first motivate our approach by showing that if a group is re-keyed on each membership change, as the size of the group increases and/or the rate at which members leave and join the group increases, the frequency of rekeying becomes the primary bottle neck for scalable group re-keying. In contrast, Kronos can scale to handle large and dynamic groups because the frequency of re-keying is independent of the size and membership dynamics of the group. Next, we describe how Kronos can be used in conjunction with distributed key management frameworks such as IGKMP (T. Hardjono et al., 1998) that use a single group-wide session key for encrypting communications between members of the group. Using a detailed simulation, we compare the performance tradeoffs between Kronos and other key management protocols.

A 1200 bps speech coder based on MELP

Abstract: This paper presents a 1.2 kbps speech coder based on the mixed excitation linear prediction (MELP) analysis algorithm. In the proposed coder, the MELP parameters of three consecutive frames are grouped into a superframe and jointly quantized to obtain a high coding efficiency. The interframe redundancy is exploited with distinct quantization schemes for different unvoiced/voiced (U/V) frame combinations in the superframe. Novel techniques for improving performance make use of the superframe structure. These include pitch vector quantization using pitch differentials, joint quantization of pitch and U/V decisions and LSF quantization with a forward-backward interpolation method. Subjective test results indicate that the 1.2 kbps speech coder achieves approximately the same quality as the proposed federal standard 2.4 kbps MELP coder.

Method of extracting text present in a color image

Abstract: The present invention is a method of extracting text from a color image by receiving a color image made up of pixels in any color component system, converting the color image to a grayscale image by performing one to five conversion methods, comparing the grayscale images to a user-definable threshold, and turning the grayscale images into binary images that may be further processed by an optical character reader or a search engine.

Cryptographic method using modified fractional fourier transform kernel

Abstract: The present invention is a cryptographic method that uses at least one component of a modified fractional Fourier transform kernel a user-definable number of times. For encryption, a signal is received; at least one encryption key is established, where each encryption key includes at least four user-definable variables that represent an angle of rotation, a time exponent, a phase, and a sampling rate; at least one component of a modified fractional Fourier transform kernel is selected, where each component is defined by one of the encryption keys; and the signal is multiplied by the at least one component of a modified fractional Fourier transform kernel selected. For decryption, a signal to be decrypted is received; at least one decryption key is established, where each decryption key corresponds with, and is identical to, an encryption key used to encrypt the signal; at least one component of a modified fractional Fourier transform kernel is selected, where each component corresponds with, and is identical to, a component of a modified fractional Fourier transform kernel used to encrypt the signal; and dividing the signal by the at least one component of a modified fractional Fourier transform kernel selected.

Interoperable secure voice communications in tactical systems

Abstract: With the increased dependence on peace-keeping operations under the auspices of the UN and NATO, interoperability among and between coalition member nations is imperative. An essential element is to overcome differences in voice coding algorithms from system to system and nation to nation. Our goal is to ensure interoperability between communications equipment produced by different nations designed to common standards. Tactical environments are very often characterized by harsh acoustic environments, and stressed or jammed channels. The next generation tactical communications systems are conceived with interoperability as a primary consideration. A key step is to adopt a single high performance voice coding algorithmic suite. This suite must be capable of multiple transmission rates which can dynamically adapt to available bandwidth, channel SNR, or by user direction. Integrating powerful forward error correction codes will optimize the system quality of service, delivered to the user by selecting the optimal combined voice and channel coding for a given impaired scenario. Most importantly, this adaptation must occur seamlessly, dynamically and instantaneously. This paper discusses one voice coding technology, the enhanced mixed excitation linear prediction, MELPe voice coding algorithmic suite, where it is today, and the additions under development and in consideration. (13 pages)

Adding immersion to collaborative tools

Abstract: While three dimensional collaborative environments have been used for industrial design or interactive games, workgroup collaboration has largely remained in the two-dimensional realm. In this paper, we examine the collaborative capabilities of the Collaborative Virtual Workspace, and how it is used. We then describe our effort to augment this system with an immersive display. By developing an immersive interface to an existing collaboration tool rather than adding collaboration to an immersive world, we hope to discover the advantages and pitfalls that immersive collaboration environments might offer. The first step in this process is to design the immersive environment to provide natural interactions for the activities users normally perform while working within the collaborative environment.

Method of multi-dimensionally accentuating a deviation in information and identifying its cause

Abstract: The present invention is a method of accentuating a deviation in a set of information and locating a cause thereof that includes the steps of receiving a set of information; selecting a subset of information; setting initial states; setting transition states; initializing a vector; selecting the first information segment; modifying the vector if the information segment contains an initial and transition state, otherwise stopping; selecting the next available information segment and returning to the previous step, otherwise recording a number of occurrences of each unique vector; determining the number of the least occurring vector; dividing each occurrence number by the least occurring number; determining an occupation time for each vector; calculating an inverse characteristic time for each unique vector; calculating at least one subset value for the subset of information using a temperature-based function, an entropy-based function, an energy-based function, or any combination thereof; setting a value vi for each initial and transition state; calculating a configuration value for each initial and transition state; selecting the subset of information then is available and next in sequence and returning to the vector modification step for further processing, otherwise plotting the subset and configuration values; finding a difference, if any, in the plotted values; and finding the information segments that correspond to the difference.

Ridge laser with oxidized strain-compensated superlattice of group III-V semiconductor

Abstract: A ridge laser that includes a Group III-V semiconductor material substrate; a first selectively oxidized at least one strain-compensated superlattice of Group III-V semiconductor material; a multiple quantum well active region; a second selectively oxidized at least one strain-compensated superlattice of Group III-V semiconductor material; a Group III-V semiconductor material cap layer; and a contact material. Each at least one strain-compensated superlattice includes at least two monolayers of a Group III-V semiconductor material and at least two monolayers of an aluminum-bearing Group III-V semiconductor material. In the preferred embodiment, the substrate is InP of any type; each selectively oxidized at least one strain-compensated superlattice of Group III-V semiconductor material is InAs/AlAs, where each at least one superlattice of InAs/AlAs includes at least two monolayers of InAs and at least two monolayers of AlAs; the multiple quantum well active region is InGaAsP lattice matched to the InP substrate, the Group III-V semiconductor material cap layer is InP, and the contact material is gold.

Method of extracting text from graphical images

Abstract: A method for extracting text from images whereby the intensity of each color plane of the image is identified, the color plane with the highest intensity is converted into a black and white image, and character recognition is performed on the black and white image to determine the text of the image The method can be used for textual word searches for Graphics Image Format (GIF) images as well as Joint Photographic Experts Group (JPEG) images, thereby providing the capability to perform text searches for images found on web pages of the World Wide Web

Baer subgeometry partitions

Abstract: For any odd integern ≥3 and prime powerq, it is known thatPG(n−1, q2) can be partitioned into pairwise disjoint subgeometries isomorphic toPG(n−1, q) by taking point orbits under an appropriate subgroup of a Singer cycle ofPG(n−1, q2). In this paper, we construct Baer subgeometry partitions of these spaces which do not arise in the classical manner. We further illustrate some of the connections between Baer subgeometry partitions and several other areas of combinatorial interest, most notably projective sets and flagtransitive translation planes.

Vertical cavity surface emitting laser with oxidized strain-compensated superlattice of group III-V semiconductor

Abstract: A vertical cavity surface emitting laser that includes a Group III-V semiconductor material substrate; a first Distributed Bragg Reflector mirror, where the first Distributed Bragg Reflector mirror includes at least seven pairs of layers, where each layer has a different index of refraction, where one of the layers is a Group III-V semiconductor material, and where the other layer is a completely oxidized at least one strain-compensated superlattice of Group III-V semiconductor material, where each at least one strain-compensated superlattice includes at least two monolayers of a Group III-V semiconductor material and at least two monolayers of an aluminum-bearing Group III-V semiconductor material; a first Group III-V semiconductor material layer; a first contact; a selectively oxidized at least one strain-compensated superlattice of Group III-V semiconductor material, where each at least one strain-compensated superlattice of Group III-V semiconductor material includes at least two monolayers of a Group III-V semiconductor material and at least two monolayers of an aluminum-bearing Group III-V semiconductor material; a second Group III-V semiconductor material layer; a second contact; and a second Distributed Bragg Reflector mirror that is identical to the first Distributed Bragg Reflector mirror.

Method of displaying real and imaginary components of a waveform

Abstract: The present invention is a method of obtaining a time history of a signal without having to integrate information on magnitude versus time and phase versus time by separately displaying sets of real and imaginary components of a signal verses time, including the steps of sampling the signal in time, where each time sample of the signal is described by a real and imaginary component; selecting a size of a display on a screen; determining the real and imaginary components for each time sample of the signal; selecting a user-definable number of samples to be displayed at any one instance; and displaying each time sample according to its real component along the X-axis, the imaginary component along the Y-axis, and the time associated with the time sample along the Z-axis.

Error coding strategies for MELP vocoder in wireless and ATM environments

Abstract: The U.S. Government has developed a new military standard (U.S. MilStd3005) 2400 bps voice coding algorithm known as MELP (mixed excitation linear prediction). This vocoder has quite acceptable voice quality and intelligibility under benign error channel conditions. However, when it is subjected to high error rates (due to noise and fading) as may be experienced in tactical wireless operations, amelioration techniques can be utilized which take advantage of the underlying inter-frame residual redundancy statistics of the specific MELP parameters. In wireless ATM system implementations, the vocoder error correction and amelioration technique must deal with the potential loss of ATM cells (in addition to the traditional RF impairments). This paper describes simulation experiments conducted on the MELP vocoding algorithm in both scenarios and notes that optimization strategies are highly dependent on both the error coding overhead allowed and the expected nature of the bitstream error and loss statistics. (33 pages)

Method of identifying boundary of markerless codeword

Abstract: The present invention is a method of determining codeword boundary without marker bits by receiving transmission bits; determining a dual code of a code used to generate the transmission bits; selecting a vector from the dual code; initializing n scoring variables; initializing i=1; initializing z=1; selecting n bits from the transmission bits starting at bit position i; performing a bit-wise AND operation on the vector and the n selected bits; if the result of the bit-wise AND operation contains an even number of ones then assigning a value of zero to the result, otherwise assigning a value of one to the result; setting S z equal to S z plus the result of the last step; if z is less than n, incrementing z and i each by 1 and returning to the seventh step, otherwise proceeding to the next step; if z=n, i

Device for converting multiple signal types to NRZ format with automatic self-test

Abstract: The present invention is a device for converting an input signal of various formats to NRZ format in a user-selectable format with automatic self-testing, that includes at least one first channel, where each first channel includes a comparator, an activity detector, an inverter, and a driver circuit, where the comparator is configured for different signal types; at least one second channel, where each second channel includes a transformer, a digitizer, an activity detector, a decoder, a framer, a clock and data recovery circuit, a first driver circuit, and a second driver circuit, having an input connected to the second output of the clock and data recovery circuit, and having an output; at least one third channel, where each third channel includes a transformer, a digitizer, an activity detector, a decoder, a clock and data recovery circuit, a first driver circuit, and a second driver circuit; at least one fourth channel, where each fourth channel includes a transformer, a fanout circuit, a digitizer, an activity detector, a serial to parallel converter, a decoder, a clock and data recovery circuit, at least one first driver circuit, and at least one a second driver circuit; a controller; a multiplexer; a demultiplexer; a comparator array; and a lamp array.

Device for dispersion compensation using tapered single-mode optical fiber

Abstract: A device for compensating for dispersion that includes a single-mode optical fiber consisting of a core, and a cladding, where the fiber has five section, a first section of a user-definable length; a second section of a user-definable length that is tapered at a user-definable rate to a user-definable diameter; a third section of a user-definable length and user-definable cutoff wavelength that is of a diameter equal to that which the second section was tapered; a fourth section of a length equal to the length of the second section, where the fourth section is tapered at the same, but opposite, rate of taper as the second section to a diameter equal to the diameter of the first section; a fifth section of a length equal to the length of the first section, and where the fiber has a user-definable cutoff wavelength. In a second embodiment, two spatial-mode converters are included with the fiber. In a third embodiment, a core-block is induced in the fiber. In other embodiments, a polarizer and a polarization rotator are included in the previous embodiments.

Method of feature extraction using combination of wavelet and fourier transformation

Abstract: The present invention is a method of removing at least one feature from a signal by receiving the signal in the time domain; identifying at least one frequency to be removed; identifying a number of resolution levels to which the signal will be reduced using wavelet transformation; computing at least one wavelet difference coefficient for each resolution level and at least one wavelet average coefficient for the lowest resolution level; creating a projection of each at least one frequency onto the lowest resolution level using Fourier transformation; subtracting the projection from the corresponding at least one wavelet average coefficient; and adding the results of the last step to the at least one wavelet difference coefficient.

Method of testing a randomizer

Abstract: A method of testing a randomizer having at least one source of probabilistic data and a device for mixing the probabilistic data to form random data, where the probabilistic data includes at least two states, by receiving a probability of occurrence of each of the at least two states in the probabilistic data; squaring each probability of occurrence; generating a row vector a of the results of the last step; receiving a probability of transition between each of the at least two states in the probabilistic data; squaring the transition probabilities; generating a matrix B of the results of the last step; generating a column vector c having entries equal in number to the at least two states in the probabilistic data, where each entry is 1; computing S(P)=a(B{circumflex over ( )}(L−1))c for each at least one source of probabilistic data, where L is a number of outputs of probabilistic data processed by the randomizer to produce m bits of output; if the at least one source of probabilistic data is greater than 1 then generating a product of the results of the last step and designating the product as S(P); computing S(Q)=(½{circumflex over ( )}m)[1+(2{circumflex over ( )}m−1)S(P)]; and declaring the randomizer acceptable if S(Q) is below a user-definable value, otherwise declaring the randomizer unacceptable.

Filter system for information network traffic

Abstract: A hardware-only filter system for controlling data packet traffic across a computer network, characterized by the provision of a grid having columns and rows, a grid populating device for introducing into the squares of the grid, respectively, binary numbers that are a function of the comparison between an incoming packet and the column and row headers of the grid. The insertion of the binary numbers into the square of the grid is controlled by an offset positioning device containing predetermined offset instructions. When the squares of any given column are all positive matched values, the filter system is operable to pass the entire approved packet.

Method of oxidizing strain-compensated superlattice of group III-V semiconductor

Abstract: A method of forming a native oxide from at least one strain-compensated superlattice of Group III-V semiconductor material, where each at least one superlattice includes two monolayers of a Group III-V semiconductor material and at least two monolayers of an aluminum-bearing Group III-V semiconductor material. The method entails exposing each at least one superlattice to a water-containing environment and a temperature of at least about 425 degrees Celsius to convert at least a portion of said superlattice to a native oxide. The native oxide thus formed is useful in electrical and optoelectrical devices, such as lasers.

Database Security 2000

Abstract: Database systems are being more and more used, with larger sized databases, and as components of very complex systems, that include numerous protocols. Database security problems in the past have only partially been solved. Is there any hope to provide adequate security for the new database systems? This paper describes user and system requirements and provides a list of hints and techniques to better secure this type of system.

Timer circuit utilizing thermal effect

Abstract: A timer circuit that utilizes the thermal runaway effect, and includes a switch, a resistor, a transistor and a protective device. The temperature of the transistor rises due to a phenomenon known as the thermal runaway effect, which causes the temperature of the transistor to rise while increasing current flow. This will eventually cause the protective device to activate. The time it takes to activate the protective device is predictable for a given transistor, therefore the circuit operates as a timer. In an alternate embodiment, a heat source is used. This heat source rises in temperature as current flows in the circuit. A heat sensor located near the heat source rises in temperature along with the heat source. A comparator compares the temperature from this heat sensor with the temperature of a heat sensor located further from the heat source. When there is a user-definable difference in temperature due to thermal diffusion between the two heat sensors, power to the transistor is disconnected. Since the heat sensors will change temperature at a predictable rate depending on the type of sensor and distance from the heat source, this circuit acts as a timer.