TECHNOLOGY

How does public key authentication work?

Last updated:

Public key authentication is a security method that uses two linked keys—a public key that anyone can see and a private key that only you have—to verify your identity and encrypt information. When you log in, the system confirms you have the matching private key without ever seeing it.

Continue in Reels Listen and swipe through more answers in Technology
Two Key TypesPublic key (shared with everyone) and private key (kept secret)
Common UseLogging into computers, servers, and online accounts securely
Encryption MethodUses complex math problems that are easy one way but extremely hard to reverse
Security AdvantageYour private key never needs to be shared or transmitted
Real-World ExampleSSH keys used to access web servers without typing passwords

How the Two Keys Work Together

Public key authentication relies on a pair of mathematically connected keys. Your public key is like a mailbox that anyone can put mail into, while your private key is like the only key that opens that mailbox. Information encrypted with your public key can only be decrypted with your private key, and vice versa. This relationship means the system can verify that you have the private key without ever actually seeing it.

The Login Process

When you try to log in to a server, the system sends you a challenge—a unique piece of information encrypted with your public key. You use your private key to decrypt and sign this challenge, then send it back. The server verifies that your response matches what should have happened only if you have the correct private key. If it matches, you're allowed access.

Why It's More Secure Than Passwords

Public key authentication is more secure than passwords because you never have to send your private key over the internet or share it with anyone. Hackers cannot intercept a password because none is being transmitted. Even if someone gets your public key, they cannot use it to log in as you—they would need the private key, which only you have. This makes it extremely difficult for unauthorized people to gain access to your accounts.

Setting Up Public Key Authentication

To use public key authentication, you first generate a key pair on your computer. The system creates both a public and private key. You then upload or register your public key with the service you want to access, such as a web server or online platform. Your private key stays on your computer and never gets shared. From that point on, you can log in using your keys instead of a password.

Common Applications

Public key authentication is widely used for accessing remote servers through SSH (Secure Shell), managing code on GitHub, securing email communication, and protecting sensitive accounts. Many organizations require it for employees to log into work computers and systems. It is considered a security best practice for protecting important accounts and systems.

Sources

  1. nist.gov (nist.gov)
  2. wikipedia.org (wikipedia.org)
  3. ssh.com (ssh.com)
  4. github.com/docs (github.com/docs)
  5. owasp.org (owasp.org)