A study on pseudo random-based symmetric block cipher encryption scheme

• Main Authors: Hsu-Tung Jhou, 周旭東
• Other Authors: Chen-Hua Fu
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/30741494888101813673

碩士 === 國防管理學院 === 國防資訊研究所 === 96 === As information security becomes more important, many encryption mechanisms were proposed to assure confidentiality of documentations. Encryption mechanisms can be divided into two branches, symmetric encryption and asymmetric encryption. Block cipher is one of major symmetric encryption schemes, another scheme is stream cipher. So far, Advanced Encryption Standard (AES) is a famous block cipher; it is accepted as one of block cipher schemes which are more secure and more reliable. This study tries to base on AES to propose an AES-alike block cipher scheme with pseudo random number generator. In the proposed encryption scheme, 3 measures, byte substitution, block scramble, and add round keys with XOR, are adopted sequentially to perform encryption process. In the decryption process, the 3 measures will be performed in an inverse sequence to decrypt ciphertexts. Moreover, the 3 measures operations require their corresponding parameters, substitution box / inverse substitution box, shift settings, and round keys, to process encryption / decryption operations. These encryption / decryption parameters are generated with a LCG random number generator. For ensuring to generate the same random number serial in the encryption / decryption processes, users need input the same unit code, passphrase, and timestamp as the premaster secrets in the propose encryption / decryption scheme. With the same premaster secrets, the same random number serial can be generated by the LCG random number generator to have corresponding encryption / decryption parameters. With corresponding encryption / decryption parameters, the proposed encryption / decryption scheme can encryption / decryption process well and efficiently. In this study, a prototype program is implemented with C and C# to understand the feasibility of the proposed block cipher mechanism. With the execution results, it shows that the proposed block cipher scheme can perform encryption / decryption process very well.