Dragon Stream Cipher

Dragon is a new word-based stream cipher, the components of which are designed to resist all known attacks. Traditionally stream cipher design has focussed on bit based linear feedback shift registers (LFSRs) that, although are fast, leave the cipher exposed to several attacks. Word based stream ciphers may provide a solution to this security-efficiency tradeoff.

Dragon is constructed using a single word based non-linear feedback shift register and a nonlinear filter function with memory. Dragon uses a variable length key and initialisation vector of 128 or 256 bits, and produces 64 bits of keystream per iteration. At the heart of Dragon are two highly optimised 8 × 32 s-boxes. Dragon uses simple operations on 32-bit words to provide a high degree of efficiency in a wide variety of environments, making it highly competitive when compared with other word based stream ciphers.

[ Download source: dragon.c ]

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