V2d: Block ciphers: Triple-DES (Applied Cryptography 101)

Welcome to "V2d: Block Ciphers: Triple-DES," a lecture in Alfred Menezes's "Crypto 101: Building Blocks" course. In this video, we explore the history and evolution of the Data Encryption Standard (DES), focusing on the development of Double-DES (2DES) and Triple-DES (3DES), two important symmetric-key encryption algorithms. We begin by analyzing the shortcomings of DES and the motivations for the creation of Double-DES, which attempts to enhance security by applying DES encryption twice with two different keys. However, we highlight a significant vulnerability in Double-DES—the meet-in-the-middle attack—and provide a detailed analysis of how this attack leverages time-memory tradeoffs to efficiently break the encryption, reducing the expected security level. Next, we discuss Triple-DES (3DES), an improvement on Double-DES, which applies the DES algorithm three times with either two or three different keys, significantly increasing security. We explore the increased complexity and resistance to attacks offered by Triple-DES and why it was widely used for many years in securing communications before being replaced by more modern encryption algorithms like AES. By the end of this lecture, you’ll have a solid understanding of the strengths and weaknesses of Double-DES and Triple-DES, and their place in the history of symmetric-key encryption. Lecture playlist: https://www.youtube.com/playlist?list=PLA1qgQLL41SRsHMtsb4up5fTytDeHV_yJ Course web page: https://cryptography101.ca/crypto101-building-blocks/ The slides are available on the course web page. Other cryptography courses: https://cryptography101.ca Slides 00:00 Introduction 00:13 Slide 70: Multiple encryption 02:14 Slide 71: Double-DES 04:00 Slide 72: Meet-in-the-middle attack on Double-DES 08:03 Slide 73: Number of plaintext/ciphertext pairs needed 09:11 Slide 74: Number of PT/CT pairs needed (2) 11:40 Slide 75: Analysis of the meet-in-the-middle attack 13:01 Slide 77: Analysis of the meet-in-the-middle attack (2) 18:35 Slide 78: Triple-DES 19:31 Slide 79: Triple-DES (2) 20:08 Coming up