常规隐信道下可证明安全隐写术的有效构造方法

E-cient construction of provably secure steganography under ordinary covert channels

隐写术是在看起来无害媒体中隐藏信息的科学.文中为了解决在常规隐信道下可证明安全隐写术的有效构造问题,在不依赖于任何采样假设的前提下,提供了一种基于计算不可区分的安全隐写术构造.文中结果表明,隐信道采样器中影射函数的不可区分性是安全隐写系统抵抗自适应选择隐文攻击的必要条件.在此基础上,完整地证明了l(-1+5-2)—安全隐写系统能在-1伪随机函数和-2无偏采样函数下有效地被构造,其中,-1和-2是任意两个可忽略错误,l是多项式的隐文长度.更为重要的,文中的研究不依赖于密码系统的密文伪随机性假设和完美采样假设,因此,我们的结果对于安全隐写系统的构造和隐写分析都具有现实意义.

Steganography is the science of hiding information within seemingly harmless messages or innocent media.This paper addresses the problems of e-cient construction of secure steganography in ordinary covert channels.Without relying on any sampling assumption,we provide a general construction of secure steganography under computational indistinguishability.Our results show that unpredictability of mapping function in covertext sampler is indispensable for secure stegosystem on indistinguishability against adaptive chosen hiddentext attacks.We completely prove that computationally secure steganography can be constructed on pseudorandom function and unbiased sampling function under ordinary covert channels,that is,its security is inversely proportional to the sum of errors of these two functions,as well as the length of hiddentexts.More importantly,our research is not dependent upon pseudorandom ciphertext assumption of cryptosystem or perfect sampling assumption.Hence,our results are practically useful for construction and analysis of secure stegosystems.