BOKHARI 256 has designed using the feature of some well-known stream ciphers like FRUIT, LIZARD, SOBER and Grain 128 to improve the performance. In this paper, we have proposed software-based synchronous lightweight stream ciphers, BOKHARI 256, mainly aimed for resource-constrained devices such as Radio Frequency Identification Devices (RFID) Tags, Wireless Sensor Node (WSN) and devices with limited processing capabilities, memory, power resources and the limited computational unit, insufficient wireless bandwidth and low ability to communicate and other general-purpose devices such as credit card, smart card, Personal Digital Assistant (PDA), etc. In the recent past, a few lightweight stream ciphers have been implemented for real applications. It is pertinent to note that the implementation of such reliable cryptographic primitives is extremely complicated in practice that requires small processing capacity, low volume, low area, and low power consumption. Developing a software-based synchronous stream cipher is reduced to building a pseudo-random sequence generator with specified cryptographic properties. Symmetric key cryptography is the most commonly used primitive and stream cipher, in particular, meets the requirement of such algorithms.
The proposed method is validated in terms of randomness using the statistical test suite provided by National Institute of Standards and Technology (NIST). The design possess good security and periodicity for the keystream generated. The proposed design is implemented for 8 bit, 16 bit and 128 bit key sizes in FPGA platform. 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.
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