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Attribute-based ring signatures: Security analysis and a new construction
, Article 2013 10th International ISC Conference on Information Security and Cryptology ; 2013 ; Asaar, M. R ; Salmasizadeh, M ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
In this study, we review attribute-based ring signature schemes. Our proposal presents two contributions; the first one is security analysis of Wenqiang et al.'s scheme in 2009 by presenting an attack in which we show that their scheme is forgeable. The second contribution is an efficient attribute-based ring signature scheme with constant size and constant number of pairing operations. Our scheme is unconditionally anonymous and unforgeable in the standard model. The security of our proposal is based on Static Diffie Hellman (SDH) problem. Compared with the existing attribute-based ring signature scheme with constant size, the length of the signature and the pairing operations in our scheme...
Optimal strategy for walking in streets with minimum number of turns for a simple robot
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) ; Vol. 8881, issue , 2014 , p. 101-112 ; Ghodsi, M ; Sharif University of Technology
Abstract
We consider the problem of walking a simple robot in an unknown street. The robot that cannot infer any geometric properties of the street traverses the environment to reach a target t, starting from a point s. The robot has a minimal sensing capability that can only report the discontinuities in the depth information (gaps), and location of the target point once it enters in its visibility region. Also, the robot can only move towards the gaps while moving along straight lines is cheap, but rotation is expensive for the robot. We maintain the location of some gaps in a tree data structure of constant size. The tree is dynamically updated during the movement. Using the data structure, we...
A New Scheme for Provable Secure Anonymous Proxy Signature in the Standard Model
, M.Sc. Thesis Sharif University of Technology ; Salmasizadeh, Mahmoud (Supervisor)
Abstract
In order to protect the proxy signers’ privacy, many anonymous proxy signature schemes have been proposed. As far as we know, there is no provable secure anonymous proxy signature scheme without random oracles. Because the provable security in the random oracle model has received a lot of criticism, in this thesis, the aim is proposing the first provable secure anonymous proxy signature in the standard model based on existing standard assumptions.It is shown in the standard model that, the proposal is anonymous against full key exposure and existential unforgeable with the computational Diffie Hellman (CDH) and Subgroup Hiding (SGH) assumptions in bilinear groups.To provide anonymity for proxy...