序贯LSB隐写术的提取攻击

序贯LSB隐写术在载体中通过连续LSB替换嵌入消息，其提取攻击问题本质上是消息嵌入起止点的估计问题。该文建立针对序贯LSB隐写术的提取攻击模型，将提取攻击问题转化为一类排序问题。对嵌入率未知情形，提出计算复杂度为O(n)的提取攻击算法。对嵌入率已知情形，给出计算复杂度为O(2logn)的快速提取攻击算法。实现了对序贯JSteg算法的提取攻击。

Extracting Attack to Sequential LSB Steganography

Sequential LSB steganography embeds message into cover image by sequential LSB substitution. The problem of extracting attack to sequential LSB steganography is essentially equivalent to the problem of estimating the beginning and the end of the secret message. This paper constructs an extract attack model for sequential LSB steganography, by translating the problem of extracting attack into a sort-problem. It proposes an algorithm whose complexity is O(n) when the embedding rate p is unknown and a fast algorithm whose complexity is O(2logn) when p is known. The extracting attack to sequential JSteg is successfully made.