CSCI 587 - Lecture 6 Public Key Encryption

• The Enigma revisited
• Alan Turing
• DES
  • Secret-key or symmetric-key cryptography
  • Adopted as Federal standard in 1976 by NBS
  • Modes
    • Electronic Code Book (ECB) - encode 64 bit block with 56 bit key
    • Cipher Block Chaining (CBC) - XOR block with previous block before encoding
  • DES algorithm
    • 16 iterations
    • f
  • DES Controversy
    • NSA hand in specifications
    • key space too small
• RSA
  • Rivest, Shamir, Alderman 1978
  • public key encryption

  • Finding a key pair

  • encryption

  • decryption

  • 1000 times slower than DES
  • RSA and DES together
• Digital signatures
• Unix: passwords, crypt, vi -x, crack
• PGP: Phil Zimmerman's Pretty Good Protection
• Clipper Chip: trapdoor
• Digital cash:

• Concordance Computations

• Text Collation

• Authorship Analysis