LM.Lecture9 - Distributed Operating Systems CS551 Colorado...

Info iconThis preview shows pages 1–14. Sign up to view the full content.

View Full Document Right Arrow Icon
Distributed Operating Systems CS551 Colorado State University at Lockheed-Martin Lecture 9 -- Spring 2001
Background image of page 1

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

View Full DocumentRight Arrow Icon
11 April 2001 CS-551, Lecture 9 2 CS551: Lecture 9 Topics Distributed Security (Chapter 11) Authentication Access Controls (Firewalls) Other Algorithms
Background image of page 2
11 April 2001 CS-551, Lecture 9 3 Terms Computer security : “frequently consists of two parts: authentication and access control” Authentication : “involves the verification and identification of a valid user” Access control : “strives to prevent unwanted tampering with data files and system resources”
Background image of page 3

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

View Full DocumentRight Arrow Icon
11 April 2001 CS-551, Lecture 9 4 Terms, continued Encryption : “encoding data using a key in such a manner that an eavesdropper cannot easily read the data” Plaintext : “ the original data” Ciphertext : “the encrypted data” Decryption : “going from ciphertext to plaintext”
Background image of page 4
11 April 2001 CS-551, Lecture 9 5 Terms, concluded Computationally secure : “An encryption algorithm is computationally secure if the system cannot be broken by systematic analysis with available resources.” Private key versus public key Symmetric versus asymmetric encryption
Background image of page 5

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

View Full DocumentRight Arrow Icon
11 April 2001 CS-551, Lecture 9 6 Simple Encryption Cereal box code ring See Java assignment on encryption Caesar cipher Polyalphabetic cipher
Background image of page 6
11 April 2001 CS-551, Lecture 9 7 Figure 11.1 Alice and Bob Use Cryptography. Read I as J in Cypher text
Background image of page 7

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

View Full DocumentRight Arrow Icon
11 April 2001 CS-551, Lecture 9 8 Symmetric Encryption “encryption algorithms where the encryption and the decryption algorithm utilize the same key” Examples: Caesar cipher Polyalphabetic cipher Key must be private “Secret-key encryption” Q: how to communicate the key? Diffie-Hellman key exchange
Background image of page 8
11 April 2001 CS-551, Lecture 9 9 Figure 11.5 Diffie-Hellman Key exchange.
Background image of page 9

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

View Full DocumentRight Arrow Icon
11 April 2001 CS-551, Lecture 9 10 DES: Data Encryption Standard Popular private key encryption method US standard (NIST 1977) Based on IBM’s LUCIFER system 64-bit key (8 for error detection) Encrypts data in blocks of 64 bits 70,000,000,000,000,000 possible keys Three-phrase encryption and decryption
Background image of page 10
11 April 2001 CS-551, Lecture 9 11 DES Phase 1: Initial Permutation A permutation of the 64-bit block, changing the order of bits within each block Each 64-bits broken up into two halves L 0 , left half R 0 , right half See DES Permutation Table E.g. the new first bit was the 58 th bit The new last bit was the 7 th bit
Background image of page 11

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

View Full DocumentRight Arrow Icon
11 April 2001 CS-551, Lecture 9 12 Table 11.1 DES Initial Permutation [NIST77]. 58 50 42 34 26 18 10 2 60 52 44 36 28 20 12 4 62 54 46 38 30 22 14 6 64 56 48 40 32 24 16 8 57 49 41 33 25 17 9 1 59 51 43 35 27 19 11 3 61 53 45 37 29 21 13 5 63 55 47 39 31 23 15 7
Background image of page 12
11 April 2001 CS-551, Lecture 9 13 DES Phase 2: Shifting (16 times) Table-dependent Each shift uses different subblock of key Which subblock is used is determined by
Background image of page 13

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

View Full DocumentRight Arrow Icon
Image of page 14
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/12/2011 for the course CS 551 taught by Professor Staff during the Summer '08 term at Colorado State.

Page1 / 66

LM.Lecture9 - Distributed Operating Systems CS551 Colorado...

This preview shows document pages 1 - 14. Sign up to view the full document.

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