As a feasible model for signing quantum messages, some cryptanalysis and improvement of arbitrated quantum signature (AQS) have received a great deal of attentions in recent years. However, in this paper we find the previous improvement is not suitable implemented in some typical AQS protocols in the sense that the receiver, Bob, can forge a valid signature under known message attack. We descri...

Dense local descriptors and machine learning have been used with success in several applications, like classification of textures, steganalysis, and forgery detection. We develop a new image forgery detector building upon some descriptors recently proposed in the steganalysis field suitably merging some of such descriptors, and optimizing a SVM classifier on the available training set. Despite ...

Proxy signature is a signature that an original signer delegates his or her signing capability to a proxy signer, and then the proxy signer creates a signature on behalf of the original signer. However, Sun et al. [7] showed that the proxy and multi-proxy signatures of Lee et al. [3], and the strong proxy signature scheme with proxy signer privacy protection of Shum et al. [6] are not against t...

This paper specializes the signature forgery by Coron, Naccache and Stern (1999) to Rabin-type systems. We present a variation in which the adversary may derive the private keys and thereby forge the signature on any chosen message. Further, we demonstrate that, contrary to the RSA, the use of larger (even) public exponents does not reduce the complexity of the forgery. Finally, we show that ou...

We study the statistical performance of spherical fingerprints for a focused detector which decides whether a user of interest is among the colluders. The colluders create a noise-free forgery by preprocessing their individual copies, and then adding a white Gaussian noise sequence to form the actual forgery. Let N be the codelength, M the number of users, and K the number of colluders. We deri...

Undoubtedly, we are living in era of digital information and technology. In this revolutionized world of digital information, we are exposed to a remarkable array of visual imagery. With sophisticated image editing tools and software‟s, it is very easy to manipulate and temper the digital images, thereby questioning the trustworthiness of it. This paper presents a method based on a statistical ...

Recently, Yang and Shieh proposed two password authentication schemes by employing smart cards. One is a timestamp-based password authentication scheme and the other is a nonce-based password authentication scheme. In 2002, Chan and Cheng pointed out that Yang and Shieh’s timestamp-based password authentication scheme was vulnerable to the forgery attack. However, in 2003, Sun and Yeh pointed o...