Understanding_Cryptography_Chptr_10---Digital signatures

Understanding_Cryptography_Chptr_10---Digital signatures -...

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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 10 – Digital Signatures ver. October 29, 2009 These slides were prepared by Georg Becker, Christof Paar and Jan Pelzl 2/26 Chapter 10 of Understanding Cryptography by 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. 3/26 Chapter 10 of Understanding Cryptography by Christof Paar and Jan Pelzl Content of this Chapter • The principle of digital signatures • Security services • The RSA digital signature scheme • The Digital Signature Algorithm (DSA) 4/26 Chapter 10 of Understanding Cryptography by Christof Paar and Jan Pelzl Content of this Chapter • The principle of digital signatures • Security services • The RSA digital signature scheme • The Digital Signature Algorithm (DSA) 5/26 Chapter 10 of Understanding Cryptography by Christof Paar and Jan Pelzl U Motivation • Alice orders a pink car from the car salesmen Bob • After seeing the pink car, Alice states that she has never ordered it: • How can Bob prove towards a judge that Alice has ordered a pink car? (And that he did not fabricate the order himself) ⇒ Symmetric cryptography fails because both Alice and Bob can be malicious ⇒ Can be achieved with public-key cryptography 6/26 Chapter 10 of Understanding Cryptography by Christof Paar and Jan Pelzl U Basic Principle of Digital Signatures 7/26 Chapter 10 of Understanding Cryptography by Christof Paar and Jan Pelzl U Main idea • For a given message x, a digital signature is appended to the message (just like a conventional signature). • Only the person with the private key should be able to generate the signature. • The signature must change for every document. ⇒ The signature is realized as a function with the message x and the private key as input. ⇒ The public key and the message x are the inputs to the verification function. 8/26 Chapter 10 of Understanding Cryptography by Christof Paar and Jan Pelzl Content of this Chapter • The principle of digital signatures • Security services • The RSA digital signature scheme • The Digital Signature Algorithm (DSA) 9/26 Chapter 10 of Understanding Cryptography by Christof Paar and Jan Pelzl U Core Security Services 1. Confidentiality : Information is kept secret from all but authorized parties....
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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_10---Digital signatures -...

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