الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 149 |  |  |
| | | from | 149 | | |
Abstract
The confidentiality and integrity processes are based on the modern SNOW / ZUC stream cipher algorithms to protect the user and signaling information transmitted over the wireless network. Both algorithms are designed by the 3rd Generation Partnership Project (3GPP) for advanced mobile communication systems (LTE Advanced-4G, LTE Advanced Pro, and Next Radio (NR)-5G).
This thesis proposes three different approaches to enhance the security level of the modern stream cipher algorithms (SNOW/ZUC) against threats of cryptanalytic attacks in advanced mobile communications.
The first approach aims to study and analyze the SNOW and ZUC algorithms, and enhancing their randomness properties of the output keystream sequences at the same time this is considered an upgrade for selecting the best combination of two S-boxes in the Finite State Machine (FSM) layer of the SNOW algorithm and in the Nonlinear Function (NLF) layer of the ZUC algorithm that achieves the best results of randomness tests according to the standardized (NIST) package. The two S-boxes are selected from the most famous S-boxes applied in cipher systems (Rijndael S-box, Dickson S-box, Feistel structure S-box, New Rijndael S-box and Improved New Rijndael S-box) which means twenty different pairwise combinations of S-boxes. Results showed that the best randomness properties lie in the combination Feistel structure (S1-box) and Rijndael (S2-box) in the SNOW algorithm and New Rijndael (S1-box) and Rijndael (S2-box) in ZUC algorithm.
The second approach increases the nonlinearity/complexity of SNOW/ZUC algorithms by selecting a strong S-box (Improved New Rijndael S-box) to cascade the existing two S-boxes for both algorithms. The upgraded SNOW/ZUC architectures in this approach passed all the NIST randomness tests successfully.
The third approach aims to increase the computational complexity of all upgraded algorithms (SNOW/ZUC) through the dynamic change of each S-box with every change of the Authentication Token (AUTN) for every user and signaling data confidentiality/ integrity process. The dynamic change S-boxes were used in all upgrades done before and passed successfully all the NIST randomness tests.
Complete simulation of these proposed upgrades is done using C language. The standardized NIST SP 800-22 statistical test suite (15 tests) is used to analyze and verify the security enhancement of the upgraded SNOW/ZUC algorithms.