Military and government institutions need security services for storing and exchanging classified information among them. Security of such information is important for independence of the State. At present, cryptography provides a lot of methods for information security. A one-time pad cipher may be used to ensure perfect (unconditional) security. There are many ciphers and other cryptographic transformations, which are not perfect, but ensure conditional security adequate to needs. All cryptosystems require keys and other crypto materials. These keys should satisfy numerous conditions. The basic is randomness. One of the best sources of random bit sequences used in the production of keys for special cryptosystems is a hardware generator. Now we have an electronic device, where it is possible to generate binary random sequences with the potential output rate of 100 Mbit/s. It gives us the capability of building an efficient key generation equipment for the cryptosystems to rely on the one-time pad cipher, where we need very long keys and for those based on symmetric or asymmetric transformations where many relatively short keys are needed.
Pseudorandom generators, which produce keystreams for stream ciphers by the exclusiveor sum of outputs of alternately clocked linear feedback shift registers, are vulnerable to cryptanalysis.In order to increase their resistance to attacks, we introduce a non-linear scrambler at the output of these generators. Non-linear feedback shift register plays the role of the scrambler. In addition, we propose Modified Alternating Step Generator with a non-linear scrambler (MASG 1S ) built with non-linear feedback shift register and regularly or irregularly clocked linear feedback shift registers with non-linear filtering functions.
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