# Public-key Cryptography

Asymmetric cryptography involves a pair of keys, one for encrypting (public) another for decrypting (private). One is private ($K^-$), the other is public ($K^+$). The key property is that one key cannot be obtained from the other in reasonable computation time

Common forms of Asymmetric Cryptography are RSA and ECC

## # Two use cases

- Sender encrypts with public key
- Only private key can decrypt it
- Used for confidentiality

- Owner encrypts with private key
- Anyone can decrypt as public key is public
- Used for authentication/proof of ownership

Can theoretically encrypt using private key but anyone with public key can decrypt!