Sharif Digital Repository

Side channel attacks, where an attacker learns some physical information about the state of a device, are one of the ways in which cryptographic schemes are broken in practice. leakage resilient ryptography addressed this issue at a higher abstraction level, proposing models capturing such attacks. Auxiliary Input is one of these models. In this thesis, we study public-key encryption schemes in this model of leakage. we also propose a method to consider this leakage continuously (i.e., not just one observation of the adversary). at the end, we consider the leakage from both the secret key owner and the encryptor. This odel captures a wider class of side-channel attacks  

Designing efficient and secure electronic voting protocols without the presence of trusted authorities, which are known as decentralized voting protocols, is one of the most interesting and challenging problems in cryptography. In these protocols the outcome of the protocol is determined by voters collaborating with each other. Since voting is a significant concept in every society, the correctness and security of voting protocols are important. For security analysis of electronic voting protocols, an intuitive proof is not enough and we require a comprehensive approach that provides provable security. In this thesis, we use universal composition framework to analyze a decentralized e-voting... 

Human has different emotions such as happiness, sadness, anger, etc. Recognizing these emotions plays an important role in human-machine interface. Emotion recognition can be divided into approaches, physiological and non-physiological signals. Non-physiological signals include facial expressions, body gesture, and voice, and physiological signals include electroencephalograph (EEG), electrocardiograph (ECG), and functional magnetic resonance imaging (fMRI). EEG signal has been absorbed a lot of attention in emotion recognition because recording of EEG signal is easy and it is non-invasive. Analysis of connectivity and interaction between different areas of the brain can provide useful... 

A secret sharing scheme involves a dealer who has a secret and distribute that among a set of participants, in such a way that only authorized subsets can recover the secret value. The collection of authorized subsets called the access structure and a secret sharing scheme in which unauthorized subset cannot reveal any partial information about the secret is called a perfect secret sharing scheme. One of the problems in secret sharing schemes is finding the appropriate lower bound for a parameter called the information ratio and optimizing it. A perfect secret sharing scheme is ideal when it has an optimal information ratio. In other words, if all shares have the same length as the secret,... 

Genome sequencing is one of the fundamental problems in today’s Biology. It has applications in significant problems such as finding association between an individual’s genome sequence and his phenotypes, discovering new genes, and finding evolutionary relations between organisms. Following the rapid advances in sequencing technologies and generation of a huge amount of short reads, efficient computational tools are needed for processing sequencing data. Shortness of reads is a factor that makes the task of reconstructing repetitive genomic regions complicated. In fact, the main challenge in both sequencing and resequencing problems is reconstruction of repeat regions. Common resequencing... 

Correlation-intractability is a random-oracle-like property of hash functions, so one can expect that constructions that are secure in random-oracle-model, remain secure when implemented using a correlation-intractable hash function. This is true about Fiat-Shamir transform which is a method for eliminating interaction from public-coin interactive proofs. One can see that when this method is applied to a public-coin three-round honest-verifier zero-knowledge proof, using a correlation-intractable hash function that also satisfies some mild assumption, the result is a NIZK argument. This is the basis for the correlation-intractability framework for NIZK which recently has been used to... 

A secret sharing scheme is a way to share a secret between a group of people so that only authorized subsets can retrieve the original secret. Secret sharing schemes were first introduced by Shamir and Blakley for threshold access structures. In a threshold access structure, a subset of individuals is allowed if the number of members exceeds a predetermined threshold. After Shamir, the study of general access structures was considered, and Ito, Saito, and Nishizeki proposed a way to construct a secret sharing scheme for these structures. Reducing the length of party's share in secret-sharing schemes and finding the optimal scheme for access structures has long been the focus of researchers...