**Near-Collision Attack and Collision-Attack on Double Block Length Compression Functions based on the Block Cipher IDEA**

*Donghoon Chang*

**Abstract: **IDEA is a block cipher designed by Xuejia Lai and James L. Massey
and was first described in 1991. IDEA does not vary the constant in
its key schedule. In \cite{ChYu06}, Donghoon Chang and Moti Yung
showed that there may be a weakness of hash function based on block
cipher whose key schedule does not use various constants. Based on
their result, we investigate the security of double block length
compression functions based on the block cipher IDEA such that the
key size of IDEA is 128 bits and its block length is 64 bits. We use
the double block length hash functions proposed by Shoichi Hirose in
the second hash workshop in 2006 \cite{Hirose06}. Then, we can
easily find a near-collision by hand. And also, for a constant $c$
of DBL hash functions, we can find a collision by hand. This means
that the constant $c$ may be used as a trapdoor to make the attacker
find collision easily.

**Category / Keywords: **Hash Function, Collision Attack, Near Collision Attack, Block Cipher, Double Block Length Hash Function, Constant, IDEA.

**Date: **received 20 Dec 2006, last revised 24 Dec 2006

**Contact author: **pointchang at gmail com

**Available format(s): **Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

**Version: **20061224:132720 (All versions of this report)

**Short URL: **ia.cr/2006/478

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