🔑 Public and Private Keys in Asymmetric Encryption
What Is Asymmetric Encryption?
Asymmetric encryption (or public-key cryptography) uses a pair of mathematically related keys:
- A public key that can be freely shared
- A private key that must be kept secret
These keys are used together to encrypt and decrypt data or to digitally sign and verify messages.
🔐 How It Works
1. Encryption & Decryption
| Action | Key Used | Who Performs It |
|---|---|---|
| Encrypt data | Public key | Anyone |
| Decrypt data | Private key | Owner of the private key |
Example:
- Alice wants to send Bob a confidential message.
- She encrypts it with Bob’s public key.
- Only Bob’s private key can decrypt it — ensuring confidentiality.
2. Digital Signatures
| Action | Key Used | Who Performs It |
|---|---|---|
| Sign message | Private key | Sender |
| Verify signature | Public key | Receiver / anyone |
Example:
- Bob signs a document using his private key.
- Anyone with Bob’s public key can verify the signature — ensuring authenticity and integrity.
🧠 Why It’s Secure
- The private key is never shared.
- It’s mathematically infeasible to reverse-engineer the private key from the public key.
- This makes it safe to communicate securely over untrusted networks.
🔁 Summary Table
| Use Case | Public Key Used For | Private Key Used For |
|---|---|---|
| Confidential Messaging | Encrypting data | Decrypting data |
| Authentication / Signing | Verifying signature | Creating digital signature |
🔒 Real-World Applications
- TLS/HTTPS: Secure communication on the internet
- SSH: Secure access to servers
- PGP/GPG: Secure email and file encryption
- JWT Signing: Verifying identity in APIs