توصيفگر ها :
سيستم هاي رمز , دوره تناوب , كدگشايي , چندجمله اي هاي خطي , كانولوشن , توربوكدها , الگوريتم IPD , چند جمله اي هاي فيدبك , طول بيشينه , ريست كردن سريع , ماير-استافلباخ
چكيده انگليسي :
Abstract In recent years various aspects of human life have been influenced by informationtechnology Consequently the importance of infonnation transmission security hasincreased Thus the need for efficient cryptography algorithms that can satisfy specificrequirements and stand against break down attacks is felt much more than the past Among these stream ciphers because of their high speed and simple implementation have many applications in cryptosystems and their efficiency and security improvementis always under cryptanalysts consideration It s obvious that for security analysisinvestigation of different attacksis necessary In this thesis after the introduction of stream ciphers and important attacks againstthem we emphasize on the principles of correlation attacks that are among the mostimportant attacks against these systems and then invf stigate fast correlation attacks Fastcorrelation attacks based on channel convolution and block codes are studied and theresults are compared The decoding techniques used in these attacks can be divided intoone step and iterative methods Finally applying iterative decoding methods on a one step method we improve the attack performance Also the acquired results by the effectsof changing the decoding algorithm threshold and the parity check equations cardinalityare investigated and compared l J l 1 Q Ji V J J
