Asymmetric key cryptography

Key distribution is a big problem, to defeat cryptography we can usually discover the key instead of cracking the cipher.

Ideally we can send encrypted messages around without having pre-shared a secret key, we can do this with asymmetric encryption. Keys now come in two parts: public and private.

To send a confidential message:

• Alice sends Bob $C=E(P,K_{\text{public}})$
• Bob decrypts $C=D(C,K_{\text{private}})$

Where $(K_{\text{public}},K_{\text{private}})$ is Bob’s key pair.