The growing applications of Mobile Ad hoc Network (MANET) has made the security issue increasingly more important. B. Zhu et al. proposes a key management scheme using Shamir's secret sharing scheme to construct an Autonomous Key Management (AKM)hierarchy structure. However, Shamir's secret sharing in AKM to control key hierarchy needs larger message transmission costs. In this paper, we modify the secret sharing scheme and apply it to AKM for reducing communication and computation cost.

In recent years, the target of the denial-of-service attacks, such as the Http flooding attack, have been switched from the network layer to the application layer. Various attacking schemes are adopted by the attackers to break down the Web site server, some of them send tremendous amount of packets to break down the target host, others send specific request packets to keep the Web site server busy in performing great amount of computations or searches of the database. In order to develop a detection scheme to detect denial-of-service attacks, one needs log data for analysis of browsing behaviors of users. But suitable log data are not easy to obtain and some of available ones are out of date and are not appropriate for analyzing behaviors of present networks. So, we propose an access log generator to generate access logs with characteristics of browsing behaviors for the particular Web site under investigation. We also include malicious behaviors into the generated access log, which is combined with actual access log of the Web site for further tests and analyses.

This study elaborates the influence patterns of different backup strategies on AODV-based routing protocols. Although some backup routing strategies yield good data delivery rates, they suffer from low efficiency. To make the process of data salvation more efficiently in case of link failure, we explore the possibility of combining the AODV-BR strategy and on-demand node-disjoint multi-path routing protocols. This article proposes an improved approach named NDAMR (node-disjoint alternative multiple path), a routing protocol that maintains the only two shortest backup paths in the source and destination nodes. The NDAMR can alleviate the redundancy-frames overhead during the process of data salvation by the neighboring intermediate nodes. Our simulation results have demonstrated that NDAMR delivers good data delivery performance while restricting the impacts of transmission collision and contention.

An improved scheme for integrity protection of binary images representing text documents based on the topologies of these images is proposed. The image skeleton and the inverse skeleton are found through thinning and the skeleton signature is combined with watermark information. The result is encrypted asymmetrically and hidden in embeddable locations of the image. A series of attack experiments are conducted to demonstrate that the approach is capable of detecting tampering. Even single malicious pixel modifications are detected. The approach has a lower computation cost than previous methods.

Multiparty key agreement has many applications on internet services such as secure teleconferencing. A group of users can hold a conference securely over an open network by running a multiparty key agreement protocol to generate a common secret key. With the common secret key, data transmission over the internet is protected for confidentiality. In 2003, Barua (INDOCRYPT 2003) first proposed a multiparty key agreement protocol by using Weil pairing. The protocol is based on ternary trees and Joux's tripartite key agreement. However, in Barua's protocol the communication round for n entities is [log3n], which is proportional to the number of participants. In this paper, we propose a new multiparty key agreement protocol from Weil pairing that needs only constant number of rounds. Besides, the message size, the total number of scalar multiplications, and the number of Weil pairing are reduced.

Based on the factorization problem, a modified (t, n) threshold group-oriented scheme with message recovery is proposed. In the proposed scheme, any combination of more than t members of the group can cooperate to generate the modified group secret key. By using the proposed scheme, the transmission of the signature is secure. Besides, the message linkage blocks which are removed by an eavesdropper can be detected.

Most of existing user authentication schemes require high computation cost of exponentiation operations for the purpose of security. However, it is not suitable for mobile devices. In this article, we propose a low computation cost user authentication scheme for mobile communication. Our scheme uses only one-way hash functions and smart cards and can be implemented efficiently. The proposed scheme not only resolves the weakness appeared in existing methods but also suits for mobile communication.

In 2004, Chang et al. suggested an approach that solves the problem of secret sharing with access structures in a hierarchy. They used the concept of discrete logarithm to reuse shadows, and adopted Cho's (Cho et al., 2001) mechanism to achieve the properties of hierarchical key management. However, Chang's scheme requires a lot of time for computation. In this paper, we adopt one-way hash function to allow the shadows to be reused and achieve the properties of hierarchical access control. The proposed scheme is more efficient than Chang's scheme.

In 2000, Joux proposed a one-round protocol for tripartite Diffie-Hellman. In 2003, Shim presented an efficient one-round tripartite authenticated key agreement protocol based on Weil pairing to resist the man-in-the-middle attack appears in Joux's. In this paper, we show that Shim's protocol still cannot withstand the insider attack and the key-compromise impersonation attack. We propose a secure one-round tripartite authenticated key agreement protocol to solve the existed problems.

In a secret sharing scheme based upon access structures, each group has an authorization and only the participants who stayed in an authorized access structure can recover the secret key. In this paper, we proposed an efficient scheme for secret sharing based upon access structures. We use one-way hash functions to reduce the cost of secret sharing scheme. The presented scheme is easy and efficient, so it is suitable for many real applications.

The concept of hierarchical access control is that a higher privileged user (or higher level) has the ability to access data in lower privileged user (or lower level). Hierarchical key management scheme is used to accomplish this concept. Each user has its secret key which is used to protect data. User at higher level can compute the secret key of a user at lower level, but the counter measurement is infeasible. There have been many proposed solutions. In this paper, we introduce an efficient way using symmetric key cryptosystem to reduce the time of generating and deriving keys in hierarchical key management, and we show that the proposed scheme retains the same security level.

We propose a secret sharing scheme with the property of access structures in a hierarchy. We employ the concept of admission tickets to delegate the access right from ancestors to their descendants. Each participant group has an authorized access structure and each access structure has its own secret key. The presented scheme is based on general hierarchies, and may be more suitable for real applications.

A new remote password authentication scheme based on IC cards is proposed in this paper. By using the scheme, a remote password can be authenticated without either a password file or a verification table. A user first applies for an account in the financial organization and then uses the given IC card to login. In the login phase, a user inputs the identity and password, transmits the generated values to the center. In the authentication phase, the system uses the secret key and remotely submitted message to verify whether the request is legal or not. A one-time-used random number and a timestamp are supplied to protect the potential attacks, which may replay a previously intercepted login request. Further, by using the characteristics of IC cards, the proposed scheme is very suitable for authenticating passwords remotely.

A key agreement protocol is utilized in a network system such that two users are able to establish a commonly shared secret key. Entities within the same security level can communicate securely with each other by using the session key. In this paper, we will propose an approach to solve the problem of supervising secure communication in a level-based hierarchy. In the proposed scheme, any two users with the same security level can efficiently establish a session key and both of them can apply it to encrypt (or decrypt) the communication messages. Accordingly, a user with higher security level can conveniently derive the session key and supervise the communication. The security of the proposed scheme is based on Diffie-Hellman's key agreement and RSA's scheme. To reveal the session key, a malicious user has to solve the factorization and the discrete logarithm problems.

In the applications of multimedia communication, besides the content-based authentication, the user authentication is also an important issue to protect the multimedia resources. We improve a fingerprint-based remote user authentication proposed by Lee, Ryu and Yoo (Electron. Lett., vol. 38, no. 12, pp. 554-555, 2002). The scheme is novel by introducing a fingerprint-based verification into authentication scheme using smart cards. However, their scheme is vulnerable to masquerade attack. In this article, we propose an improved scheme to enhance the security of their scheme in order to overcome the vulnerability. Our scheme protects the host resources which can only be accessed by authorized users.

The multiplications of common multiplicands and exponentiations of large integers with large modulus are the primary computation operations in several well-known public key cryptosystems. The Hamming weight of the multiplier or the exponent plays an important role for computation efficiency. By performing complements, the Hamming weight of an integer can be reduced. Based on this concept, we propose efficient algorithms for common-multiplicand multiplications (CMM) and exponentiations. In the average case, it takes k/2+2/spl times/log(k)+5 k-bit additions to compute the CMM. For exponentiation, the proposed method takes 5k/4+2 multiplications on average, but the pre-computation for a modular multiplicative inverse is required. Combining the original CMM, the number of multiplications can further be reduced to 9k/8+2.

Harn (1994) proposed a signature scheme based on the modified ElGamal scheme and claimed that the security relies on both the factorization and the discrete logarithm. That is, his scheme cannot be broken unless both of the above two problems can be solved simultaneously. Lee and Hwang (1996) showed that an attacker could generate a forged signature on the assumption when the discrete logarithm is solved. Recently, Shao (1998) proposed another two signature schemes, which the security rests on the two problems. In this paper, we propose two improved signature schemes that are really based on two hard problems simultaneously. In addition, the numbers of parameters and computations are reduced in comparison with those of Shao.

In this paper, we combined the public secrete key cryptograph system proposed by Diffie and Hellman, with the infinite generation keys based on grey theory. And we got another related code for cryptograph system. This is a kind of infinite generation keys based on the public key system. This system is much more secret than traditional systems, and it can also be applied in then. According to past researches, Diffe and Hellman had presented the basic concepts of cryptography, based on the discrete logarithm model. Another search in grey field, only a few papers has touch this field. It is the first time that AGO method applied in grey theory in this kind of research. Also, based on the GM(1,1) model, we used finite original code to create an infinite variables code sequence, and we got the code from the known secrete key. In this paper, we define two parameters: cryptography sequence /spl psi/ and 3rd order symmetric group S/sub 3/ and presented six cryptography models to contribute our system. Based on discrete logarithm model, the secrete value is high to O(e/sup C/spl radic/(ln(p)ln(ln(p)))/) for public system, and it is hard to calculate the sequence by the present computing ability. Therefore, to break into this system by mathematical formula is not possible nowadays. To promote the efficiency, we also develop a toolbox not only to decrease the calculation time, but also to examine the reliability of our system.

A new public-key (two-key) cipher scheme is proposed in this paper. In our scheme, keys can be easily generated. In addition, both encryption and decryption procedures are simple. To encrypt a message, the sender needs to conduct a vector product of the message being sent and the enciphering key. On the other hand, the receiver can easily decrypt it by conducting several multiplication operations and modulus operations. For security analysis, we also examine some possible attacks on the presented scheme.>

The encryption/decryption scheme proposed in8 is generalised in this paper. The new cryptosystem presented is record-oriented, i.e. each record is encrypted integratedly with different keys and each field is decrypted individually by separate keys, and has significant advantages over many conventional methods. Compared to the encryption system proposed by Davida, Wells, and Kam,8 this new system has the advantages the previous one has and improves two drawbacks of theirs which will be stated below. Thus not only the security is increased but also the storage needed is reduced in the new cryptosystem.