TAILIEUCHUNG - Lecture Data security and encryption - Lecture 8: Data encryption standard (DES)

This chapter presents the following content: Data encryption standard (DES), strengths of DES, differential & linear cryptanalysis, block cipher design principles, the AES selection process, the details of Rijndael – the AES cipher, looked at the steps in each round. | Data Security and Encryption (CSE348) Lecture slides by Lawrie Brown for “Cryptography and Network Security”, 5/e, by William Stallings, briefly reviewing the text outline from Ch 0, and then presenting the content from Chapter 1 – “Introduction”. Lecture # 8 Review Data Encryption Standard (DES) DES Encryption Initial Permutation IP DES Round Structure Substitution Boxes S DES Key Schedule DES Example Avalanche in DES Strength of DES Chapter 3 summary. Differential Cryptanalysis Biham & Shamir show Differential Cryptanalysis can be successfully used to cryptanalyse the DES with an effort on the order of 247 encryptions Rerequiring 247 chosen plaintexts Although 247 is certainly significantly less than 255 Biham & Shamir show Differential Cryptanalysis can be successfully used to cryptanalyse the DES with an effort on the order of 247 encryptions, requiring 247 chosen plaintexts. Although 247 is certainly significantly less than 255, the need for the adversary to find 247 chosen plaintexts makes this attack of only theoretical interest. They also demonstrated this form of attack on a variety of encryption algorithms and hash functions. Differential cryptanalysis was known to the IBM DES design team as early as 1974 (as a T attack), and influenced the design of the S-boxes and the permutation P to improve its resistance to it. Compare DES’s security with the cryptanalysis of an eight-round LUCIFER algorithm which requires only 256 chosen plaintexts, verses an attack on an eight-round version of DES requires 214 chosen plaintexts. Differential Cryptanalysis The need for the adversary to find 247 chosen plaintexts makes this attack of only theoretical interest They also demonstrated this form of attack on a variety of encryption algorithms and hash functions Differential cryptanalysis was known to the IBM DES design team as early as 1974 (as a T attack) Biham & Shamir show Differential Cryptanalysis can be successfully used to

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