The key exchange problem describes ways to exchange whatever keys or other information are needed for establishing a secure communication channel so that no one else can obtain a copy.

  • Alice locks the box with her lock and sends it to Bob
  • Bob locks the box with his lock and sends it back to Alice
  • Alice removes her lock and sends it back to Bob
  • Bob removes his lock
  • Double Encryption Transfer
    • Both parties generate random keys and
    • Sender sends encrypted message
    • Receiver encrypts received message and sends it back
    • Sender decrypts message and sends it again (only valid if operation is associative!)
    • Receiver decrypts final message

Diffie Hellman

A way of performing key exchange over an insecure channel.