Research On The Security Detection Method Of Block Ciphers Based On FPGA

Block cipher that belongs to symmetric ciphers is an important means to protect the information security. Are there any vulnerabilities, and how to find out them? Both of them are the mainly problems of cryptanalysis.FPGA as programmable logic devices is widely applied to code implementation and analysis because of its advantages, such as flexible programming, fast processing speed,short design cycle, low cost, strong real-time validation.The security detection methods of some block ciphers(i.e. AES, SIMON and SPECK)are investigated. The main results are following:1. Aspect of detection and analysis of key neutral-bit for reduced round AES: Basing on the key scheme and the round function structures, we design a cube neutral-bit detection algorithm for AES-128 by using FPGA test platform. Our simulation results show neutral secret key bits exist in the output bits of 3-round AES-128 if the cubic variables are fixed in the range of 17 to 24 dimensions. However, the case doesn’t exist for 4-round AES-128.It directly means that there is good characteristic of both confusion and diffusion in the full-round AES-128 for all secert key bits.2. Aspect of cube test and analysis for reduced SIMON family of block ciphers: By both combining the basic idea of the cube attack and cube test, we propose a SIMON32/64 cube attack and a cube neutral-bit detection algorithm by using FPGA test platform. The results show that: for 7-round SIMON32/64 algorithm, 48-bit key can be recovered directly with a data complexity of about17.152 chosen plaintexts and a time complexity of about17.712 encryptions by using cube attack. Moreover, for 8-round SIMON32/64 algorithm, 32-bit key can be directly recovered and 4 linear equations on another 6 bits of the secret key can be found with a data complexity of about15.482 chosen plaintexts and a time complexity of about28.002 encryptions by using cube attack. Therefore, it means that cube attack pose actual threat to lower reduced-round SIMON32/64. With regard to9-round SIMON32/64 algorithm, neutral secret key bits can be captured by using cube test.Moreover it is shown that SIMON32/64 can achieve the full confusion and diffusion when iteration number is larger than 10 rounds.3. Aspect of cube test and analysis of block cipher SPECK: For 3-round SPECK32/64 algorithm, 17-bit key can be recovered directly with a time complexity of about47.002 encryptions and a data complexity of about10.022 chosen plaintexts by combining quadraticity tests with cube attack. Therefore, we conclude that SPECK32/64 caneffective resist the combine quadraticity tests with cube attack, when iteration number is larger than 4 rounds. With regard to 5-round, 6-round SPECK32/64 algorithm, neutral secret key bits can be captured by using cube test. Moreover this shows that the algorithm of SPECK32/64 can be confused and diffused fully when iteration number is larger than 7rounds.