cryptography full report

[seminar class]

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ITNS and CERIAS CISSP Luncheon Series: Cryptography
 Introduction
 “Hidden writing”
 Increasingly used to protect information
 Can ensure confidentiality
• Integrity and Authenticity too
 History – The Manual Era
 Dates back to at least 2000 B.C.
 Pen and Paper Cryptography
 Examples
• Scytale
• Atbash
• Caesar
• Vigenère
 History – The Mechanical Era
 Invention of cipher machines
 Examples
• Confederate Army’s Cipher Disk
• Japanese Red and Purple Machines
• German Enigma
 History – The Modern Era
 Computers!
 Examples
• Lucifer
• Rijndael
• RSA
• ElGamal
• Speak Like a Crypto Geek
Plaintext – A message in its natural format readable by an attacker
Ciphertext – Message altered to be unreadable by anyone except the intended recipients
Key – Sequence that controls the operation and behavior of the cryptographic algorithm
Keyspace – Total number of possible values of keys in a crypto algorithm
 Speak Like a Crypto Geek (2)
Initialization Vector – Random values used with ciphers to ensure no patterns are created during encryption
Cryptosystem – The combination of algorithm, key, and key management functions used to perform cryptographic operations
 Cryptosystem Services
 Confidentiality
 Integrity
 Authenticity
 Nonrepudiation
 Access Control
 Types of Cryptography
 Stream-based Ciphers
 One at a time, please
 Mixes plaintext with key stream
 Good for real-time services
 Block Ciphers
 Amusement Park Ride
 Substitution and transposition
 Encryption Systems
 Substitution Cipher
 Convert one letter to another
 Cryptoquip
 Transposition Cipher
 Change position of letter in text
 Word Jumble
 Monoalphabetic Cipher
 Caesar
 Encryption Systems
 Polyalphabetic Cipher
 Vigenère
 Modular Mathematics
 Running Key Cipher
 One-time Pads
 Randomly generated keys
 Steganography
 Hiding a message within another medium, such as an image
 No key is required
 Example
 Modify color map of JPEG image
 Cryptographic Methods
 Symmetric
 Same key for encryption and decryption
 Key distribution problem
 Asymmetric
 Mathematically related key pairs for encryption and decryption
 Public and private keys
 Cryptographic Methods
 Hybrid
 Combines strengths of both methods
 Asymmetric distributes symmetric key
» Also known as a session key
 Symmetric provides bulk encryption
 Example:
» SSL negotiates a hybrid method
 Attributes of Strong Encryption
 Confusion
 Change key values each round
 Performed through substitution
 Complicates plaintext/key relationship
 Diffusion
 Change location of plaintext in ciphertext
 Done through transposition
 Symmetric Algorithms
 DES
 Modes: ECB, CBC, CFB, OFB, CM
 3DES
 AES
 IDEA
 Blowfish
 Symmetric Algorithms
 RC4
 RC5
 CAST
 SAFER
 Twofish
 Asymmetric Algorithms
 Diffie-Hellman
 RSA
 El Gamal
 Elliptic Curve Cryptography (ECC)
 Hashing Algorithms
 MD5
 Computes 128-bit hash value
 Widely used for file integrity checking
 SHA-1
 Computes 160-bit hash value
 NIST approved message digest algorithm
 Hashing Algorithms
 HAVAL
 Computes between 128 and 256 bit hash
 Between 3 and 5 rounds
 RIPEMD-160
 Developed in Europe published in 1996
 Patent-free