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.

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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.

The capacity and security of the confidential message on the channel are two important challenges in steganography. In this paper, a new block steganography model is presented using the bargain method so that a competitive model is introduced. In this game, the blocks are the same players. The bargain is provided with the aim of embedding information without reducing capacity as well as increasing security. The proposed model shows that it can be used both of the special domain and the transform domain, which are two important methods of steganography. For this purpose, an example of a special domain model is introduced in which, In the first step, the image is divided into n × n blocks, and in the second step using the graph coloring algorithm, pixels are considered to embed confidential information in each block. In the third step, regarding the bargaining method in game theory, each block plays the role of a player, that the competition between players is based on the defined goal function, and in the best blocks in terms of two criteria of capacity and security, which here means each block has a higher security-to-capacity ratio, so it has a higher priority, which is determined based on the bargaining model. Also, information embedded in LSB two bits. An example of a conversion domain method is also shows that security increases without decreasing in capacity. The conclusion is evaluated by three criteria: PSNR, histogram, and − secure also, 2000 standard images were evaluated and observed that the proposed method improves the block methods of embedding information.