Reza Ebrahimi Atani

  Final Defense session of The PhD Thesis

  Abstract:

  Stream ciphers are fast cryptographic primitives to provide confidentiality of electronically transmitted data. They can be very suitable in environments with restricted resources, such as mobile devices or embedded systems. Practical examples are cell phones, RFID transponders, smart cards or devices in sensor networks. Besides efficiency, security is the most important property of a stream cipher.

  In the thesis first we address the classical methods in design and analysis of stream ciphers. The third section of this thesis specifies Alamout, a new hardware oriented synchronous stream cipher with an associated authentication mechanism. The design is small in hardware and it targets environments with limited resources. Alamout supports key size of 80 bits and IV size of 128 bits. The Alamout cipher has been designed to produce keystream with guaranteed randomness properties. Simulation with ENT randomness test program confirms randomness of output keystream with very good results

 The threat of DPA attacks is of crucial importance when designing cryptographic hardware. The forth chapter of the thesis discusses the DPA-resistant implementation of two eSTREAM finalists using SABL and WDDL logic styles. Particularly, two Feedback Shift Register (FSR) based stream ciphers, Grain v.1 and Trivium are designed in both BSim3 130nm and typical 350nm technologies and simulated by HSpice software. Circuit simulations and statistical power analysis show that DPA resistivity of SABL implementation of both stream ciphers has a major improvement.

  In the next chapter of this thesis a compact implementation of the SBox of Pomaranch stream cipher using composite field arithmetic in 12GF((23)3)'> is presented. It describes a systematic exploration of different choices for the irreducible polynomials that generate the extension fields. It also examines all possible transformation matrices that map one field representation to another. We evaluated the optimal candidates using Xilinx and Altera FPGA implementations. And finally in the last section of the thesis two public key cryptography protocols are introduced: Public key cryptography based on semi modules over quotient semi rings and also Public Key Cryptography using Semi-Group Actions and Semi-Rings.