Parallel generation of c[r]yptographically strong pseudo-random sequences

The operational disadvantages of perfectly secure cipher systems has led to the development of practically secure stream cipher systems. The security of such cipher systems depend on the strength of the keystream. In order to examine the strength of a sequence two different types of criteria are considered. Statistical tests, are designed to assess how a sequence with a particular property behaves randomly. Complexity measures, are applied to determine the complexity, or equivalently the unpredictability of a sequence. Sequences obtained by LFSR are considered as building blocks of pseudo-random (PR) sequence generators. Transformations on the decimal expansion of irrational numbers is an alternative method for generating PR sequences, which are studied and some encouraging results are reported

Kodierungstheorie

[no abstract available

Trellis phase codes for power-bandwith efficient satellite communications

Support work on improved power and spectrum utilization on digital satellite channels was performed. Specific attention is given to the class of signalling schemes known as continuous phase modulation (CPM). The specific work described in this report addresses: analytical bounds on error probability for multi-h phase codes, power and bandwidth characterization of 4-ary multi-h codes, and initial results of channel simulation to assess the impact of band limiting filters and nonlinear amplifiers on CPM performance

Advanced modulation technology development for earth station demodulator applications

The purpose of this contract was to develop a high rate (200 Mbps), bandwidth efficient, modulation format using low cost hardware, in 1990's technology. The modulation format chosen is 16-ary continuous phase frequency shift keying (CPFSK). The implementation of the modulation format uses a unique combination of a limiter/discriminator followed by an accumulator to determine transmitted phase. An important feature of the modulation scheme is the way coding is applied to efficiently gain back the performance lost by the close spacing of the phase points