Sharif Digital Repository

The lightweight blockciphers and lightweight authenticated encryptions are special kind of the symmetric schemes designed to use in cases that resources such as power, area, etc. are limited. Sensor Networks and RF-Tags are two good example of lightweight schemes application. This limitations force designers to use simpler functions and operators in comparison to conventional schemes; therefore, providing the security in this case is so important. A novel approach for evaluating security of an algorithm is to apply different kinds of attack. Impossible differential cryptanalysis is one of the shortcut cryptanalysis, using the impossible differential characteristic. Impossible differential... 

Due to the ever-increasing growth of the ubiquitous computing systems such as RFID, IoT, etc. and their important security concerns specially in the domain of user’s privacy, a great attention from the cryptology community is attracted to the design and analysis of lightweight primitives. Lightweight primitives, including block ciphers, hash functions, stream ciphers, and authenticated encryption schemes, are those ones that are specifically tailored to the devices with extreme limitations in power, area and cost. It is natural that the conventional rules for designing a typical all-purpose primitive can not be used here identically, and designers have to relax the conditions of some... 

Block ciphers are the central tool in the design of security protocols. GOST is a block cipher that several attacks have been published on it during the past 20 years. One of them is the reflection attack that was first introduced in 2007. This attack utilizes similarities of some round functions of both encryption and decryption processes. In addition, there are approaches that combines techniques of the reflection attack and variants of the meet-in-the-middle attack. In this thesis, we study reflection-based attacks on GOST. We first describe the GOST block cipher and the reflection attack. Then, we review previous reflectionbased attacks such as reflection-meet-in-the-middle attack and... 

Along with the proliferation of pervasive systems such as RFID systems and sensor networks, the demand for the low-cost, secure-enough primitives has continued to rise. Symmetric-key algorithms especially block ciphers still play an important role as secure ciphers that can be also consistent with the inherent restrictions of pervasive systems. Recently, a lot of block ciphers tailored for these conditions have been designed, such as Present, PrintCipher, Piccolo, and Twine. Biclique attack introduced in AsiaCrypt 2011 is the first and the only method that could break all versions of AES faster than brute-force attack in the single key model. Afterwards, the efficiency of this attack on some... 

Lightweight cryptography is a branch of cryptography science which is expanded in response of security need in pervasive and lightweight systems (such as RFID systems and wireless sensor networks) in the last decade. In general, the significant challenges in designing lightweight ciphers can be attributed to three essential parameters: security, cost, and performance. Hence the main goal in designing new lightweight ciphers is to develop innovative and atypical structures in order to have a cipher with a small footprint, sufficient speed, reduced power consumption, while remaining sufficiently secure. Due to lack of proper ciphers that are both efficient and secure for constrained...