【作者】 赵元志；

【导师】 廖晓峰；

【作者基本信息】 重庆大学 ， 计算机应用技术， 2005， 硕士

【摘要】 阈下信道是指在基于公钥密码的数字签名中建立起来的一种隐蔽信道,除指定的接收者外,任何人均不知道其中是否有阈下消息存在。它是一种典型的现代信息隐藏技术,有着广阔的应用前景。本文在介绍了阈下信道产生的历史背景后,分析了美国数字签名算法(DSA)中存在的阈下信道及其特性,并对牛顿信道的特点也进行了详细介绍。本论文的研究指出椭圆曲线数字签名算法(ECDSA)与美国数字签名标准一样也存在着同样特点的阈下信道。当使用宽带阈下信道时,发信者必须把自己的签名密钥交给阈下接收者,使得阈下接收者有能力伪造发信者的签名。为了克服这个缺陷,文献[21]提出了一种新的基于ESIGN 数字签名算法的阈下信道方案。在这类阈下信道中,发信者和接收者之间不共享任何秘密密钥,从而使得阈下接收者不能伪造发信者的签名。本文也研究了阈下信道的封闭问题,讨论了封闭阈下信道的几种方法。其中,令看守参与签名生成的方案能够达到完全封闭阈下信道的目的,同时也能保证签名者的签名权力。本文所取得的主要创新成果如下: 1) 基于数字签名的形式化定义和DSS 数字签名方案,分析了阈下信道的存在机理及DSA 中的几种阈下信道的特点。2)证明了在椭圆曲线数字签名算法(ECDSA)中,不仅存在窄带阈下信道,也存在宽带阈下信道,它们与DSA 中的阈下信道的特性是相同的。更多还原

【Abstract】 The subliminal channel is a covert communication channel that constructed in the digital signature which based on the public key cryptography. In the subliminal channel, any subliminal message cannot be discovered except the authorized receiver.It is a typical modern information hiding technology and has many practical applications. In this dissertation, the background and the corresponding theories of the subliminal channel are introduced. We analyzed the character of the subliminal channel for the Digital Signature Algorithm (DSA), and also introduced the Newton Channel. The existence of the subliminal channel for the Elliptic Curve Digital Signatures Algorithm (ECDSA) was pointed out in this thesis. The channels based on DSA or ECDSA have a same disadvantage that the transmitter must send his private signature key to the subliminal receiver, which allows the subliminal receiver to forge the transmitter’s signature in the broadband subliminal channel. For overcoming this disadvantage, a new subliminal channel was embeded in the ESIGN digital signature algorithm, in which there has not common secret key between the sender and the authorized subliminal receiver. Hence, the subliminal receiver cannot forge the transmitter’s signature. The subliminal-free is also studied in this dissertation, and some schemes for the subliminal-free are carefully discussed. The scheme in which the warden attends the generation of the signature achieves the aim completely and insures the signer’s authority. The main contributions in this thesis are as follows: 1) Based on the formal definition of digital signature and the Digital Signature Algorithm(DSA) , the existence mechanism of subliminal channel and some subliminal channels in the DSA are analyzed in detail. 2) The existence of the narrow-band and the broad-band subliminal channels in the Elliptic Curve Digital Signature Algorithm (ECDSA) is pointed out in this dissertation. And the characters of the subliminal in ECDSA are as same as that in the DSA.更多还原