This paper presents an efficient approach to synchronizing two identical chaotic systems in order to achieve a cryptosystem, and this approach is intended specifically to digital communications. Instead of sending a drive signal accompanied with encrypted message to the receiver, we send only one signal which results a continuous perturbation to the chaotic system. The large computation precision used for implementation and the way by which the system key is chosen reveal high randomness of the proposed chaotic cryptosystem (PCCS) and avoid short cycles and non-chaotic regions.The mechanism used for encryption shows the reliability and efficiency of the PCCS in terms of security, and this can be proven by the failing of cryptanalysis that carried out on the PCCS and the good results of statistical tests. The real-time FPGA hardware implementation results show the efficiency of the PCCS in terms of throughput and hardware resources consumption.

<p>The developments of communications and digital transmissions have pushed the data encryption to grow quickly to protect the information, against any hacking or digital plagiarisms. Many encryption algorithms are available on the Internet, but it's still illegal to use a number of them. Therefore, the search for new the encryption algorithms is still current. In this work, we will provide a preprocessing of the securisation of the data, which will significantly enhance the crypto-systems. Firstly, we divide the pixel into two blocks of 4 bits, a left block that contains the most significant bit and another a right block which contains the least significant bits and to permute them mutually. Then make another permutation for each of group. This pretreatment is very effective, it is fast and is easy to implement and, only consumes little resource.</p>

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Mobile phones are the most common communication devices in history. For this reason, the number of mobile subscribers will increase dramatically in the future. Therefore, the determining the location of a mobile station will become more and more difficult. The mobile station must be authenticated to inform the network of its current location even when the user switches it on or when its location is changed. The most basic weakness in the GSM authentication protocol is the unilateral authentication process where the customer is verified by the system, yet the system is not confirmed by the customer. This creates numerous security issues, including powerlessness against man-in-the-middle attacks, vast bandwidth consumption between VLR and HLR, storage space overhead in VLR, and computation costs in VLR and HLR. In this paper, we propose a secure authentication mechanism based new mobility management method to improve the location management in the GSM network, which suffers from a lot off drawbacks, such as transmission cost and database overload. Numerical analysis is done for both conventional and modified versions and compared together. The numerical results show that our protocol scheme is more secure and that it reduces mobility management costs the most in the GSM network.