Cryptology ePrint Archive: Report 2005/383

Key Mixing in Block Ciphers through Addition modulo $2^n$

Debdeep Mukhopadhyay and Dipanwita RoyChowdhury

Abstract: The classical technique to perform key mixing in block ciphers is through exclusive-or (exor). In this paper we show that when the $n$-bit key is mixed in a block cipher of size $n$ bits via addition modulo $2^n$, the bias of the linear approximations falls exponentially fast. Experimental results have been provided to show that such a scheme cannot be cryptanalyzed using Linear Cryptanalysis.

Category / Keywords: secret-key cryptography / Block Ciphers, linear cryptanalysis, Key Mixing, Linear Approximations, Piling-Up Lemma

Date: received 22 Oct 2005

Contact author: debdeep at vlsi iitkgp ernet in

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Version: 20051023:210049 (All versions of this report)

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