In this paper, the Cyclic Redundancy Check (CRC) hash circuit is combined with the normal LFSR circuit and the keystream is generated by the CRC circuit. In such cases the security of the PRNG depends on the hash function used and the way in which it is used. The commonly used Linear Feedback Shift Register (LFSR) structures with inherent linearity can be used along with hash function based Pseudo Random Number Generator (PRNG) structures to increase periodicity and throughput. Stream ciphers based on hash functions are less complex in hardware and provides better security in embedded systems having space constraints.
