Error reconciliation for practical quantum cryptography

Error reconciliation is a necessary step for quantum key distribution process. In this paper, the correction ability of error reconciliation procedure which is called Winnow protocol is analyzed and estimated, moreover, it gives some expressions about it. The experiment results proved the capability of Winnow protocol are excellent. It is also indicates that the smallest N has the most correction efficiency where from the communication times between the legitimate parties and the data remaining efficiency consideration.     

Cryptanalysis and improvement of controlled secure direct communication

This paper points out that, due to a flaw in the sender＇s encoding, the receiver in Gao et al.＇s controlled quantum secret direct communication （CQSDC） protocol [Chin. Phys. 14 （2005）, No. 5, p. 893] can reveal the whole secret message without permission from the controller. An improvement is proposed to avoid this flaw.     

Information Security, Mathematics, and Public-Key Cryptography

Public-key cryptography is today recognized as an important tool in the provision of information security. This article gives an overview of the field on the occasion of its 22nd birthday.     

Expandable quantum key distribution networks based on secret bits comparison

A scheme of quantum network based on multiuser differential phase shift quantum key distribution system (DPS-QKD) is proposed. In this quantum network, arbitrary two users can achieve secret bits sharing by point-to-multipoint quantum key distribution and secret bits comparison. A protocol of secret bits sharing between arbitrary two users is presented. This network can implement secret bits distribution over 200 km with higher key generation rate by today's technologies. In theory, the capacity of user numbers in this network is unlimited. Hence, our proposed quantum network can serve for a metropolitan QKD network. A wide area QKD network can be constructed with this metropolitan QKD network.     

基于多线程的AES-ECB改进设计与性能分析

为了满足高速即时通信对密码运算的性能要求,在研究AES-ECB典型设计的基础上,提出了一种基于多线程技术的AES-ECB改进设计方案。通过对算法中间迭代过程进行分割,并将其例化为多个子线程,改进了算法运行流程,实现了子线程间的“类流水”操作。实例性能分析表明,相比于单线程,多线程性能提高了约0.46至4.27倍;当线程数为12时,算法处理性能最低为520Mbps,适用于对加解密速度要求高的应用场合。     

Improving the quantum secure direct communication by entangled qutrits and entanglement swapping against intercept-and-resend attack

The security of quantum secure direct communication by entangled qutrits and entanglement swapping [Y.B. Zhan et al., Opt. Commun. 282 (2009) 4633] is analyzed. It is shown that an eavesdropper can obtain all the secret without being found by a simple intercept-and-resend attack. Finally, a possible improvement to resist this attack is proposed.     

A Low-Memory Algorithm for Point Counting on Picard Curves

Combining the ideas of Bauer, Teske and Weng, [1] and Gaudry, Schost [3], we give a low memory algorithm for computing the number of points on the Jacobian of a Picard curve. It is efficient enough to handle Picard curves over finite prime fields , where p is a prime with 58 bits. We present an example where the Jacobian has a prime group order of size 2¹⁷⁴     

Bounds for visual cryptography schemes

In this paper, we investigate the best pixel expansion of various models of visual cryptography schemes. In this regard, we consider visual cryptography schemes introduced by Tzeng and Hu (2002) [13]. In such a model, only minimal qualified sets can recover the secret image and the recovered secret image can be darker or lighter than the background. Blundo et al. (2006) [4] introduced a lower bound for the best pixel expansion of this scheme in terms of minimal qualified sets. We present another lower bound for the best pixel expansion of the scheme. As a corollary, we introduce a lower bound, based on an induced matching of hypergraph of qualified sets, for the best pixel expansion of the aforementioned model and the traditional model of visual cryptography scheme realized by basis matrices. Finally, we study access structures based on graphs and we present an upper bound for the smallest pixel expansion in terms of strong chromatic index.     

Attacks and counter-attacks on the GPT public key cryptosystem

The public key cryptosystem based on rank error correcting codes (the GPT cryptosystem) was proposed in 1991. Several attacks against this system were published, including Gibson’s attacks and recent Overbeck’s attacks. In this paper, we improve the GPT system by more careful choice of parameters to withstand these attacks.      

A New Approach for Visual Cryptography

Visual cryptography is to encrypt a secret image into some shares (transparencies) such that any qualified subset of the shares can recover the secret visually. The conventional definition requires that the revealed secret images are always darker than the backgrounds. We observed that this is not necessary, in particular, for the textual images.In this paper, we proposed an improved definition for visual cryptography based on our observation, in which the revealed images may be darker or lighter than the backgrounds. We studied properties and obtained bounds for visual cryptography schemes based on the new definition. We proposed methods to construct visual cryptography schemes based on the new definition. The experiments showed that visual cryptography schemes based on our definition indeed have better pixel expansion in average.