Since various pseudo-random algorith ms and sequences are used for cryptography of data or as init ial values for starting a secure communicat ion, how these algorith ms are analyzed and selected is very important. In fact, given the g rowingly extensive types of pseudorandom sequences and block and stream cipher algorith ms, selection of an appropriate algorith m needs an accurate and thorough investigation. Also, in order to generate a pseudo-random sequence and generalize it to a cryptographer algorith m, a co mprehensive and regular framework is needed, so that we are enabled to evaluate the presented algorith m as quick as possible. The purpose of this study is to use a number of pseudo-random number generators as well as popular cryptography algorith ms, analyze them in a standard framework and observe the results obtained in each stage. The investigations are like a match between d ifferent algorith ms, such that in each stage, weak algorith ms are eliminated using a standard method and successful algorith ms enter the next stage so that the best algorith ms are chosen in the final stage. The main purpose of this paper is to certify the approved algorithm.

Random numbers have a significant role in cryptography, and methods of generating these numbers always require serious attention in order to ensure proper security of cryptography. In this paper, we introduce a linear congruential pseudo-random number generator that operates by utilizing chaotic maps and shift register. In each stage, LFSR's perform (XOR) sum on specific positions in the binary field. The aim of this paper is to use chaotic maps to randomly select positions at each stage, and then perform summing operation in binary field on least significant bits produced by linear congruential generator to produce a good pseudo-random sequence. In fact, weakness of linear congruential generator which is its short period and weakness of LFSR which is its linearity are both resolved by implementing chaotic maps in the design. The proposed generator merges two layers of cryptography and scrambling, which operate separately in image, audio and video signals, into one layer. Statistical analysis by NIST and DIEHARD packages and results of statistical evaluations on the quality of generator output confirm the efficiency of the proposed generator. Algorithm speed and it security in terms of key space is assessed, and given its robustness against different attacks, it can be concluded that this pseudo-random number generator is suitable for cryptography application.

Many models have been designed for generating pseudo random numbers and there is the potentiality to design more. Among the mentioned generators, a few of them are applied in cryptography. Thus, there is an inevitable need among researchers and users for evaluating the generators. A variety of criteria are used for evaluation which have more or less or neutral importance depending on the way the generators are applied. Accordingly, some reliable sources pay attention to the particular criterion while overlooking others. In the present study, in addition to enumerating all of the popular criteria, there has been an attempt to classify them in the form of a general model. At the end, some suggestions are presented for the foremost priority in using and applying the criteria. With implementing this pattern all the criterions have been considered and on the other hand the probability of second type error will be reduced. Also, observance of the sequence of criterions would cause saving in time and costs.