Public Key Cryptography The Inventors Whitfield Diffie and martin hellman 1976 Ralph merkle 1978 Trap Door Alice Bob C fKn(P) f 1 (C B B Encryption with one-way function Computation of inverse function One-way functions extremely expensive are often based on welll Joe known hard problems f KR (c) 22 Public Key Cryptography • The Inventors – Whitfield Diffie and Martin Hellman 1976 – Ralph Merkle 1978 C = fKB (P) Encryption with one-way function P = f-1 KB (C,TB) Joe P = f-1 KB (C) Alice Bob KB Computation of inverse function extremely expensive Trap Door One-way functions are often based on well￾known hard problems