Asymmetric Encryption

Asymmetric encryption, also called public-key cryptography, uses a pair of mathematically related keys: a public key and a private key. It solves the fundamental problem of symmetric encryption — how to share a secret key securely.

---

The Key Distribution Problem

With symmetric encryption, both parties need the same key. But how do you share that key securely?

• Send it by email? — can be intercepted
• Share it in person? — impractical at scale
• Use another encryption key? — who shares that one?

Whitfield Diffie and Martin Hellman solved this problem in 1976 by inventing public-key cryptography, one of the most important breakthroughs in the history of information security.

---

How Asymmetric Encryption Works

Each user generates a key pair:

Key	Properties
Public key	Shared openly with anyone
Private key	Kept secret — never shared

Encryption

Sender:    Plaintext ──▶ [Encrypt with Recipient's PUBLIC key] ──▶ Ciphertext
Receiver:  Ciphertext ──▶ [Decrypt with Recipient's PRIVATE key] ──▶ Plaintext

Only the recipient's private key can decrypt data encrypted with their public key.

Digital Signatures (Preview)