The study of how to send messages privately and securely.
First attempt: use a secret method or key.
Two parties A and B want to communicate without C.
Simple Cipher
- assigning numbers to letters
- sending numbers
- translating via cipher
Book Cipher
- numbers assigned to book
- C can invert process if has the same book
- Utilizes the same language
One time pad: random string as the book text
- requires meetup irl
- long
Public Key Cryptography
- A encrypts message with B’s public key, and B decrypts with their secret key.
- No private exchange necessary!