National Security Agency

About: National Security Agency is a government organization based out in Fort George Meade, Maryland, United States. It is known for research contribution in the topics: Signal & Encryption. The organization has 393 authors who have published 485 publications receiving 15916 citations. The organization is also known as: NSA & N.S.A..

Satisfiability and Computing van der Waerden Numbers

Abstract: In this paper we bring together the areas of combinatorics and propositional satisfiability. Many combinatorial theorems establish, often constructively, the existence of positive integer functions, without actually providing their closed algebraic form or tight lower and upper bounds. The area of Ramsey theory is especially rich in such results. Using the problem of computing van der Waerden numbers as an example, we show that these problems can be represented by parameterized propositional theories in such a way that decisions concerning their satisfiability determine the numbers (function) in question. We show that by using general-purpose complete and local-search techniques for testing propositional satisfiability, this approach becomes effective — competitive with specialized approaches. By following it, we were able to obtain several new results pertaining to the problem of computing van der Waerden numbers. We also note that due to their properties, especially their structural simplicity and computational hardness, propositional theories that arise in this research can be of use in development, testing and benchmarking of SAT solvers.

Handling nominal features in anomaly intrusion detection problems

Abstract: Computer network data stream used in intrusion detection usually involve many data types. A common data type is that of symbolic or nominal features. Whether being coded into numerical values or not, nominal features need to be treated differently from numeric features. This paper studies the effectiveness of two approaches in handling nominal features: a simple coding scheme via the use of indicator variables and a scaling method based on multiple correspondence analysis (MCA). In particular, we apply the techniques with two anomaly detection methods: the principal component classifier (PCC) and the Canberra metric. The experiments with KDD 1999 data demonstrate that MCA works better than the indicator variable approach for both detection methods with the PCC coming much ahead of the Canberra metric.

Method of protecting a computer stack

Abstract: A method of protecting a return address on a computer stack is disclosed. Two stacks are created, the first a normal stack, and the second, or shadow, having shadow frames containing the return address upon a subroutine call, the address on the first stack where the return address is stored, and a user-definable state variable which is used to identify a shadow frame as a return address. Before returning from a subroutine, the two return addresses are compared, and if they do not match, the second stack is searched down, and then up, for a matching return address. If there is a match, the shadow is re-synchronized with the first stack by comparing the stored values of the first stack pointer with the first stack pointer and adjusting appropriately the shadow stack pointer. The matching shadow frame must also be a return address datatype of return address.

On designs and formally self-dual codes

Abstract: Binary formally self-dual (f.s.d.) even codes are the one type of divisible [2n, n] codes which need not be self-dual. We examine such codes in this paper. On occasion a f.s.d. even [2n, n] code can have a larger minimum distance than a [2n, n] self-dual code. We give many examples of interesting f.s.d even codes. We also obtain a strengthening of the Assmus-Mattson theore. IfC is a f.s.d. extremal code of lengthn≡2 (mol 8) [n ≡6 (mod 8)], then the words of a fixed weight inC ∪C ⊥ hold a 3-design [1-design]. Finally, we show that the extremal f.s.d. codes of lengths 10 and 18 are unique.

Rf power harvesting circuit

Abstract: Provided is an RF power harvesting circuit with improved sensitivity to RF energy. The RF power harvesting device includes an inductor, a first capacitor connected to the inductor, a first MOSFET connected to a first node, and a second MOSFET connected to the first node. The inductor or the first capacitor are connected to the first node.