Ch 20 Encryption

Block Encryption Algorithms

DES

3DES or Triple DES

AES

Symmetric Stream Algorithms

RC4

Symmetric Encryption

Application:

Cryptography

Types of operations

Number of keys used

text processing type

Substitution (Confusion)

Transposition (Deffusion)

single-key, symmetric, secret-key, conventional

two-key, asymmetric, public-key

stream cipher

block cypher

Modes of Operation

Electronic Codebook

Cipher Block Chaining

Cipher Feedback

Counter

Plaintext: 64 bit

Key: 56 bit

Blocks: 64 bit

16 Rounds

16 Subkeys

Follows FCS closely

Feistel Cipher Structure

Plaintext: 64 bit

Key: 168, 112 bit

Blocks: 64 bit

16 Rounds

16 Subkeys

Does DES 3 times

Plaintext: 128 bit

Key: 128, 192, 256 bit

Blocks: 128 bit

10,12,14 Rounds

44 Subkeys

New Matrix algorithm

Different decryption alg.

A block of text encoded with the same key intependantly

not used

encoding of XOR of previous sypher text and new plane text block

rarely used

encrypt counter

convers to stream sypher

Galois Counter

Counter mode with message authentication

most internet traffic is this plus AES as encryption alg

Converts to stream cypher

Hash Functions

Asymmetric Encryption

Applications

Key management

Digital signatures

Applications