Secure key distribution is critical
With a symmetric system like DES, Alice and Bob have to agree on a shared secret.
- Doesn’t work well on a large scale
- Doesn’t work with people who haven’t met in advance
But there is a great idea:
Diffie-Hellman key agreement (1976):
Alice and Bob can create a shared secret key by exchanging messages, even though everyone can eavesdrop on the messages!