基于非0比特个数特征的冗余转移图像加密安全性分析

Security Analysis of Image Encryption for Redundant Transfer Based on Non-Zero-Bit Number Feature

Qin等人提出的基于冗余转移的高容量加密域可逆信息隐藏算法,有效提高了抵抗现有已知明文和唯密文等攻击的能力.在分析该算法的冗余转移图像加密特性的基础上,提出一种基于非0比特个数(non-zero-bit number,NZBN)特征的已知明文攻击方法.首先,定义给出了图像块的NZBN特征,分析指出了图像块NZBN特征在冗余转移图像加密前、后的恒定不变性;然后利用NZBN特征的恒定不变性,依次估计块置乱密钥和每个图像块的位平面置乱密钥;接着,给出了多对明密文图像条件下的块置乱密钥估计方法,以进一步提高块置乱密钥的估计正确率;最后,分析讨论了在不同分块大小下的密钥估计正确率和时间复杂度.实验结果表明,算法的密钥估计正确率和时间复杂度依赖于分块大小.分块大小不小于4×4时,1对明密文图像得到的块置乱密钥正确率超过89%;即使分块大小降至2×2,2对明密文图像可导致信息泄露.

A encryption algorithm named redundant transfer based on high-capacity reversible data hiding in encrypted images scheme was proposed by Qin et al,which effectively improved the ability to resist existing known-plaintext and cipher-only attacks.Based on the analysis of the redundant transfer image encryption characteristics,a known-plaintext attack method is proposed based on the non-zero-bit number(NZBN).Firstly,the NZBN feature of the image block is defined,and the analysis points out the constant invariance of the NZBN feature of image block before and after the redundant transfer image encryption.And then,the block scrambling key and the bit-plane scrambling key of each image block are estimated in turn by using the invariance of the NZBN feature.Next,the block scrambling key estimation method under the condition of multiple pairs of plain-ciphertext images is given to further improve the estimation accuracy of the block scrambling key.Finally,the key estimation accuracy and time complexity of the proposed method are discussed under different block sizes.Experimental results demonstrate that the key estimation accuracy and time complexity of the algorithm depend on the block size.When the block size is not less than 4×4 pixels,the correct rate of block scrambling key obtained from a pair of plain-ciphertext images exceeds 89%.Even if the block size is reduced to 2×2 pixels,two pairs of plain-ciphertext images may cause information leakage.