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CAvium – Strengthening Trivium Stream Cipher Using Cellular Automata
Sandip Karmakar, Debdeep Mukhopadhyay and Dipanwita Roy Chowdhurys

Cellular Automata configurations are known to be able to generate good pseudorandom sequences. Linear Cellular Automata and LFSRs are equivalent in pseudorandom sequence generation, but those structures could be easily cryptanalysed due to their lack of nonlinearity. It is noted in this paper that introduction of both nonlinear and linear rules in Cellular Automata structures can reach the desired setup state of a cipher much faster than the LFSR and NFSR based contemporary systems and provides secure design. The eStream cipher Trivium, in spite of being secure in its full round operation, till date, faces a large number of cryptanalysis on reduced versions of it. Trivium also has a long key setup process. In the present paper, we present a modification of the Trivium stream cipher using Cellular Automata which strengthens it against almost all the attacks encountered against reduced rounds of Trivium, so far. The modification, CAvium also decreases the time required for startup from 1152 to 144 rounds. Finally, we show that CAvium and Trivium have comparable complexity in hardware implementations.

: Cellular Automata, Stream Cipher, Trivium, Cryptography, Cellular Automata based Stream Cipher, Strengthening Trivium

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