Understanding_Cryptography_Chptr_5---More_about_Block_Ciphers

Understanding_Cryptography_Chptr_5---More_about_Block_Ciphers

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Unformatted text preview: Understanding Cryptography – A Textbook for Students and Practitioners by Christof Paar and Jan Pelzl www.crypto-textbook.com Chapter 5 – More About Block Ciphers ver. November 26, 2010 These slides were prepared by Amir Moradi, Christof Paar and Jan Pelzl Some legal stuff (sorry): Terms of Use • The slides can used free of charge. All copyrights for the slides remain with Christof Paar and Jan Pelzl. • The title of the accompanying book “Understanding Cryptography” by Springer and the author’s names must remain on each slide. • If the slides are modified, appropriate credits to the book authors and the book title must remain within the slides. • It is not permitted to reproduce parts or all of the slides in printed form whatsoever without written consent by the authors. 2/38 Chapter 5 of Understanding Cryptography by Christof Paar and Jan Pelzl 3/38 Chapter 5 of Understanding Cryptography by Christof Paar and Jan Pelzl Content of this Chapter • Encryption with Block Ciphers: Modes of Operation • Electronic Code Book mode (ECB) • Cipher Block Chaining mode (CBC) • Output Feedback mode (OFB) • Cipher Feedback mode (CFB) • Counter mode (CTR) • Galois Counter Mode (GCM) • Exhaustive Key Search Revisited • Increasing the Security of Block Ciphers U Block Ciphers • A block cipher is much more than just an encryption algorithm, it can be used ... • to build different types of block-based encryption schemes • to realize stream ciphers • to construct hash functions • to make message authentication codes • to build key establishment protocols • to make a pseudo-random number generator • ... • The security of block ciphers also can be increased by • key whitening • multiple encryption 4/38 Chapter 5 of Understanding Cryptography by Christof Paar and Jan Pelzl 5/38 Chapter 5 of Understanding Cryptography by Christof Paar and Jan Pelzl Content of this Chapter • Encryption with Block Ciphers: Modes of Operation • Electronic Code Book mode (ECB) • Cipher Block Chaining mode (CBC) • Output Feedback mode (OFB) • Cipher Feedback mode (CFB) • Counter mode (CTR) • Galois Counter Mode (GCM) • Exhaustive Key Search Revisited • Increasing the Security of Block Ciphers U Encryption with Block Ciphers • There are several ways of encrypting long plaintexts, e.g., an e-mail or a computer file, with a block cipher (“modes of operation”) • Electronic Code Book mode (ECB) • Cipher Block Chaining mode (CBC) • Output Feedback mode (OFB) • Cipher Feedback mode (CFB) • Counter mode (CTR) • Galois Counter Mode (GCM) • All of the 6 modes have one goal: • In addition to confidentiality, they provide authenticity and integrity: • Is the message really coming from the original sender? (authenticity) • Was the ciphertext altered during transmission? (integrity) 6/38 Chapter 5 of Understanding Cryptography by Christof Paar and Jan Pelzl 7/38 Chapter 5 of Understanding Cryptography by Christof Paar and Jan Pelzl...
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This note was uploaded on 04/01/2011 for the course MA C taught by Professor Anario during the Spring '11 term at Universitat Politècnica de Catalunya.

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Understanding_Cryptography_Chptr_5---More_about_Block_Ciphers

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