Public Key Cryptography

• Each participant has
  • public key - released to others
  • secret key - kept secret
  • Example Alice (P_A, S_A), Bob (P_B, S_B)
• Public and Secret functions are inverses
  • M = S_A(P_A(M))
  • M = P_A(S_A(M))
• Must be able to reveal P_A while S_A remains uncomputable (or at least very difficult to compute).
• Security depends on method of computing keys
  • RSA - factoring large integers
  • McEliecee - decoding linear code (NP-Complete)
  • El Gamal - discrete logarithm problem
  • Chor-Rivest - knapsack (NP-Complete)