## Cryptology ePrint Archive: Report 2007/397

**On the security defects of an image encryption scheme**

*Chengqing Li, Shujun Li, Muhammad Asim, Juana Nunez, Gonzalo Alvarez and Guanrong Chen*

**Abstract: **This paper studies the security of a recently-proposed chaos-based
image encryption scheme, and points out the following problems: 1)
there exist a number of invalid keys and weak keys, and some keys
are partially equivalent for encryption/decryption; 2) given one
chosen plain-image, a subkey $K_{10}$ can be guessed with a smaller
computational complexity than that of the simple brute-force attack;
3) given at most 128 chosen plain-images, a chosen-plaintext attack
can possibly break the following part of the secret key: $\{K_i\bmod
128\}_{i=4}^{10}$, which works very well when $K_{10}$ is not too
large; 4) when $K_{10}$ is relatively small, a known-plaintext
attack can be carried out with only one known plain-image to recover
some visual information of any other plain-images encrypted by the
same key.

**Category / Keywords: **secret-key cryptography / cryptanalysis

**Date: **received 6 Oct 2007

**Contact author: **swiftsheep at hotmail com

**Available format(s): **PDF | BibTeX Citation

**Version: **20071014:185211 (All versions of this report)

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