Defence Research Agency

About: Defence Research Agency is a based out in . It is known for research contribution in the topics: Synthetic aperture radar & Radar. The organization has 1211 authors who have published 1109 publications receiving 31542 citations.

Current Dependence of Small Signal Base - Collector Capacitance in Microwave AlGaAs/GaAs HBTs

Abstract: The current dependence of small signal base-collector capacitance, C bc and base series resistance, R b , extracted directly from S-parameters, has been investigated in microwave n-p-n AlGaAs/GaAs HBTs. It is found that the magnitude of C bc at V ce =3V in our devices is relatively constant at low current densities but reduces at current density of 2×103A/cm2 and then increases rapidly at a critical value of 3×104A/cm2. The results obtained are compared with a physics based analytical model and shown to exhibit good agreement.

Fast time series adaptive filtering algorithms based on the QRD inverse-updates method

Abstract: We derive, from first principles, a new adaptive filtering algorithm for time-series data based on the QRD inverse-updates method of Pan and Plemmons. In common with other fast algorithms for time-series adaptive filtering, this algorithm only requires O(p) operations for the solution of pth order problem. Unlike previous fast algorithm based on the QRD technique, the algorithm presented here (in both square-root and square-root-free forms) explicitly produces the transversal filter weights. The results of some preliminary computer simulations of the algorithm, using finite-precision floating-point arithmetic, are presented.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Attribute pooling for Cryptographic Access Control

Abstract: The need to securely share classified information is a long-standing open problem, especially in large and dynamic environments. Multiple large scale approaches, such as NATO Object Level Protection (OLP) and Content-based Protection and Release (CPR) address parts of this problem. CPR contains an example for enforcement paradigm called Cryptographic Access Control (CAC), to enable combining protection and release policies with content, user and terminal properties (or attributes) cryptographically. The main element of CAC in this case is called attribute-based encryption, or ABE. With ABE it is possible to enforce very fine-grained policies, but combining attributes from users and terminals for general policies is cumbersome and not directly possible with existing schemes. We present in this paper a key-management encryption scheme on top of a multi-authority ABE solving the key pooling problem. Direct applications include a more efficient and general CAC approach for e.g. CPR to enable more secure handling of multi-level secure, encrypted content. Indirectly, the more general framework of CAC itself is completed with this functionality.