Understanding_Cryptography_Chptr_13---Key_Establishment

Understanding_Cryptography_Chptr_13---Key_Establishment -...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Understanding Cryptography by Christof Paar and Jan Pelzl www.crypto-textbook.com Chapter 13 – Key Establishment ver. Jan 7, 2010 These slides were prepared by Christof Paar and Jan Pelzl
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
s The slides can used free of charge. All copyrights for the slides remain with Christof Paar and Jan Pelzl. s The title of the accompanying book “Understanding Cryptography” by Springer and the author’s names must remain on each slide. s If the slides are modified, appropriate credits to the book authors and the book title must remain within the slides. s It is not permitted to reproduce parts or all of the slides in printed form whatsoever without written consent by the authors. Some legal stuff (sorry): Terms of Use 2/27 Chapter 13 of Understanding Cryptography by Christof Paar and Jan Pelzl
Background image of page 2
s Introduction s The n 2 Key Distribution Problem s Symmetric Key Distribution s Asymmetric Key Distribution - Man-in-the-Middle Attack - Certificates - Public-Key Infrastructure U Content of this Chapter 3/27 Chapter 13 of Understanding Cryptography by Christof Paar and Jan Pelzl
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
U Classification of Key Establishment Methods In an ideal key agreement protocol, no single party can control what the key value will be. 4/27 Chapter 13 of Understanding Cryptography by Christof Paar and Jan Pelzl
Background image of page 4
It is often desirable to frequently change the key in a cryptographic system. Reasons for key freshness include: - If a key is exposed (e.g., through hackers), there is limited damage if the key is changed often - Some cryptographic attacks become more difficult if only a limited amount of ciphertext was generated under one key - If an attacker wants to recover long pieces of ciphertext, he has to recover several keys which makes attacks harder U Key Freshness 5/27 Chapter 13 of Understanding Cryptography by Christof Paar and Jan Pelzl
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
U Key Derivation s In order to achieve key freshness, we need to generate new keys frequently. s Rather than performing a full key establishment every time (which is costly in terms of computation and/or communication), we can derive multiple session keys k ses from a given key k AB . s The key k AB is fed into a key derivation function together with a nonce r („number used only once“). s Every different value for r yields a different session key 6/27 Chapter 13 of Understanding Cryptography by Christof Paar and Jan Pelzl
Background image of page 6
U Key Derivation s The key derivation function is a computationally simple function, e.g., a block cipher or a hash function Alice Bob generate nonce r derive session key K ses = e kAB (r) r derive session key K ses = e kAB (r) s Example for a basic protocol: 7/27 Chapter 13 of Understanding Cryptography by Christof Paar and Jan Pelzl
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
s Introduction s The n 2 Key Distribution Problem s Symmetric Key Distribution s Asymmetric Key Distribution - Man-in-the-Middle Attack - Certificates - Public-Key Infrastructure U Content of this Chapter 8/27 Chapter 13 of Understanding Cryptography by Christof Paar and Jan Pelzl
Background image of page 8
U The n 2 Key Distribution Problem
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

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.

Page1 / 27

Understanding_Cryptography_Chptr_13---Key_Establishment -...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online