Yasmine Abouelseoud

MIDSCYK: An efficient provably secure multi-recipient identity-based signcryption scheme

Signcryption is a public key cryptographic primitive that combines the functionalities of encryption and digital signatures in a single logical step at low computational and communications costs. This paper presents a new efficient multi-recipient identity-based signcryption scheme. The scheme provides public verifiability of ciphertext origin which is an essential requirement in firewall authentication protocols. The scheme offers considerable reductions in both the computational overhead and bandwidth requirements compared to other schemes in literature. The scheme is provably secure against chosen ciphertext attacks in the random oracle model under the assumption of the hardness of the decisional bilinear Diffie-Hellman problem. Moreover, the scheme is existentially unforgeable and thus supports some sort of non-repudiation. The performance enhancements offered by the proposed scheme promote its use in several applications such as authenticated mail transfers among large mailing groups as well as virtual conference scenarios.

An Optimized Hybrid Approach for Spectrum Handoff in Cognitive Radio Networks With Non-Identical Channels

Cognitive radio (CR) is a technology that aims to enhance the use of the underutilized spectrum. Spectrum handoff plays this role by allowing the unlicensed secondary users (SUs) to use the licensed frequency bands of the primary users (PUs). Moreover, it helps the SU to vacate the channel at the presence of the PU and find a suitable channel for the interrupted SU to continue his unfinished transmission. In this paper, an analytical model for the general case of non-identical channels in CR networks is introduced for both fixed and probabilistic sequence approaches for target channel selection. Moreover, a new balancing model is suggested to generate the probabilistic sequence. Both the fixed and probabilistic sequence approaches are optimized using the meta-heuristic methods of particle swarm and genetic algorithm in the seek of finding an optimal approach to minimize the extended data delivery time of the SUs. The results are based on the pre-emptive resume priority M/M/1 queueing network model and are shown for different network cases. Based on the optimization results, a fast hybrid approach is proposed and found to achieve near optimal solution.

Certificate-based authenticated key agreement protocols

In this paper, the problem of establishing a shared session key in an authenticated way is addressed. New key agreement protocols that support explicit authentication are proposed. The protocols are designed in such a way that permits a trusted third party, such as a firewall, to verify the identities of the parties involved in a key agreement session. This is of course to reduce the computational burden at the end-user side, which can be a device with limited capabilities. The security properties of the proposed protocols are analyzed revealing the strength of these protocols promoting their use in practical scenarios such as in mobile communications.

Extension and application of El-Gamal encryption scheme

Security is an essential requirement in the industrial world. Information leakage to competitors can cause financial problems for a company. Moreover, the wide use of the Internet as an environment for doing business and shopping calls for secure electronic transactions. Confidentiality of the information is preserved through the use of encryption schemes. This paper proposes a new three-party extension of ElGamal encryption scheme and a multi-receiver extension of ElGamal encryption scheme. For both of the two proposed schemes, security and performance are analyzed. Finally, the application of El-Gamal encryption scheme in internet voting is studied for its importance nowadays.

Two-Phase Image Encryption Scheme Based on FFCT and Fractals

This paper blends the ideas from recent researches into a simple, yet efficient image encryption scheme for colored images. It is based on the finite field cosine transform (FFCT) and symmetric-key cryptography. The FFCT is used to scramble the image yielding an image with a uniform histogram. The FFCT has been chosen as it works with integers modulo and hence avoids numerical inaccuracies inherent to other transforms. Fractals are used as a source of randomness to generate a one-time-pad keystream to be employed in enciphering step. The fractal images are scanned in zigzag manner to ensure decorrelation of adjacent pixels values in order to guarantee a strong key. The performance of the proposed algorithm is evaluated using standard statistical analysis techniques. Moreover, sensitivity analysis techniques such as resistance to differential attacks measures, mean square error, and one bit change in system key have been investigated. Furthermore, security of the proposed scheme against classical cryptographic attacks has been analyzed. The obtained results show great potential of the proposed scheme and competitiveness with other schemes in literature. Additionally, the algorithm lends itself to parallel processing adding to its computational efficiency.

New blind signcryption schemes with application to E-cash systems

Signcryption is a well-known cryptographic primitive that achieves various security goals including confidentiality of communications, source authentication, and integrity of message contents and ensuring non-repudiation. In e-cash systems, customers prefer to spend their e-coins anonymously. Blind signatures have been developed to meet this requirement. In the present paper, two new blind signcryption schemes are proposed in order to combine the functionalities of both primitives in a single logical step. The first one is tailored for traditional public key infrastructures; while the second one is an identity-based scheme. The proposed schemes have been designed with an eye on applications to e-cash systems and thus overcoming shortcomings in earlier attempts in blind signcryption. The two schemes are computationally efficient promoting their use in practical scenarios. The schemes involve three parties. In e-cash scenarios, these are the bank, the e-coin acquirer (customer) and the merchant which deposits the e-coin in his bank account.

Privacy protecting digital payment system using ID-based blind signatures with anonymity revocation trustees

In this paper, a new digital payment system based on an ID-based blind signature scheme is presented. Blind signatures represent one cryptographic primitive tailored for applications where anonymity of the participants is an important requirement for instance in electronic commerce, in particular for payment systems. Since anonymity could be in conflict with law enforcement, for instance in cases of black mailing or money laundering, it has been proposed in literature to design systems in which a trustee or a set of trustees can selectively revoke the anonymity of the participants involved in a suspicious transaction. The trustee in the proposed payment system is only invoked in case of disputes and does not get involved in neither opening accounts nor issuing digital coins.

A new blind identity-based signature scheme

Anonymity of consumers is an essential functionality that should be supported in any digital rights management system. Privacy protection is an important aspect for wider acceptance of consumers of DRM systems. The concept of a blind signature is one possible cryptographic solution, yet it has not received much attention in the identity-based setting. In the identity-based setting, the public key of a user is derived from his identity, thus simplifying certificates management process compared to traditional public key cryptosystems. In this paper, a new blind identity-based signature scheme based on bilinear pairings on elliptic curves is presented. The use of bilinear pairings over elliptic curves enables utilizing smaller key sizes, while achieving the same level of security compared to other schemes not utilizing elliptic curves. The correctness of the proposed scheme is validated and the proof of the blindness property is provided. Performance and security related issues are addressed.

Mixed-integer quadratically constrained programming with application to distribution networks reconfiguration

This paper implements a mixed-integer quadratically constrained convex optimization program on distribution networks that have a radial structure topology for denigration of systems real power loss. The adopted mathematical model has been solved using Cplex optimization software. The global optimality of the obtained solution is guaranteed via convex relaxation of the continuous decision variables. This overcomes a major disadvantage of using artificial intelligence techniques, specifically meta-heuristic ones, that give no assurance on the solution quality or the optimality gap. Moreover, exact representation of the network losses through the assessment of the objectives function numerical-value is obtained. This overcomes the drawbacks of using linear approximations to power flow equations. The proposed algorithm has been evaluated on two IEEE standard systems and a realistic-sized network with a comparative study with other existing algorithms in the literature.

An efficient load flow algorithm for radial distribution networks

This paper presents an efficient load flow algorithm, specifically tailored for Radial distribution networks, which employ special recursive techniques for load flow owing to their radial topology and high (R/X) ratios of its transmission lines. The proposed methodology models the load flow problem into a convex optimization problem, which is solved using primal-dual interior-point algorithm in polynomial time. Moreover, the time draining LU decomposition techniques and forward/backward substitution algorithms of the Jacobian matrix or admittance matrix essential for the traditional load flow methods are no longer needed. A comparison between the proposed algorithm and another validated algorithm in literature has been provided to verify the computational precision of the adopted algorithm. Moreover, the proposed algorithm has shown clear competitiveness in terms of computational efficiency.