6.hash-MAC

6.hash-MAC - Cryptographic Hash Functions Message...

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

View Full Document Right Arrow Icon
Cryptographic Hash Functions Message Authentication Digital Signatures
Background image of page 1

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

View Full DocumentRight Arrow Icon
Abstract We will discuss Cryptographic hash functions Message authentication codes HMAC and CBC-MAC Digital signatures 2
Background image of page 2
Encryption/Decryption Provides message confidentiality . Does it provide message authentication ? 3
Background image of page 3

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

View Full DocumentRight Arrow Icon
Bob receives a message from Alice, he wants to know (Data origin authentication) whether the message was really sent by Alic e; (Data integrity) whether t h Message Authentication m i i message authentication code e message has been modified. Solutions: Alice attaches a (MAC) to the message. Or she attach digital signatur es a to the message. e i i 4
Background image of page 4
A hash function maps from a domain to a smaller range, typically many-to-one. Properties required of a hash function depend on its applications. Application s: Fast l o o Hash function i kup (hash tables) Error detection/correction cryptographic ha Cryp sh f tography unctions : Others i i i 5
Background image of page 5

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

View Full DocumentRight Arrow Icon
* * : , | | | |. For example, :{0,1} {0,1} {0,1} , . If Hash functi is ons: Cryptographic hash function n n kl hX Y X Y h hZ hk l X •→ > →> () finite, is also called a compression function. A classical application: users/clients passwords are stored in a file not as username, password , but as username, h h using some cryptographic hash fu (password nctio ) n . h 6
Background image of page 6
Pre-image: if ( ) , is a pre-image of . Each hash value typically has multiple pre-images. Collision: a pair of ( , ), , s.t. ( ) ( ). A hash function is said t Security requirements hm y m y mm m m •= ′′ •≠ = o be: if it is computationally infeasible to find a pre-image of a hash value. if it is computationally in Pre-image resistant C feasible to find a col ollision re lision sistant . A hash fu n cryptographic hash functio ction is a if it is collision resista n nt. 7
Background image of page 7

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

View Full DocumentRight Arrow Icon
8 Collision-resistant hash functions can be built from collision-resistant compression functions using Merkle-Damgard construction.
Background image of page 8
* * hash compression Construct a cryptographic function :{0,1} {0,1} from a function {0,1} . 1. For {0,1} , add to so that | '| is padding Merkle-Damgard construction n nb n h f mm m + •→ 12 01 a multiple of .
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 01/22/2011 for the course CSE 651 taught by Professor Tenh.lai during the Spring '10 term at Ohio State.

Page1 / 32

6.hash-MAC - Cryptographic Hash Functions Message...

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