A public key is a special code used in cryptography that you can safely share with the world so others can encrypt data for you or verify that something really came from you. It always comes in a pair with a matching private key, which you must keep secret and which is the only thing that can unlock or “undo” what was done with the public key.

What Is a Public Key? (Quick Scoop)

Think of a public key like a secure lock you give away, while keeping the only key that opens it. Anyone can use the lock to secure a message to you, but only you can open it.

Simple definition

  • A public key is a long number (or string) generated by a cryptographic algorithm as part of a key pair : public key + private key.
  • The public key can be shared with anyone, posted on servers, or embedded in certificates.
  • It is mathematically related to the private key, but practically impossible to reverse to find the private key.

In other words: public key = safe to share, private key = must stay secret.

How It Works (High Level)

Public key cryptography is also called asymmetric cryptography because it uses two different keys instead of one.

Typical flow:

  1. Key generation
    • Software generates a pair: one public key and one private key.
 * They are mathematically linked (what one does, only the other can undo).
  1. Sharing the public key
    • You publish your public key on a directory, website, or certificate so others can use it.
  1. Encryption with the public key
    • Someone who wants to send you a secret message encrypts it using your public key.
  1. Decryption with the private key
    • Only your private key can decrypt the message.

So even though the public key is open to everyone, only the holder of the private key can read messages encrypted with it.

What Can a Public Key Do?

A public key has two main jobs in modern systems.

1. Encrypt data for confidentiality

  • Anyone can use your public key to encrypt:
    • Messages (emails, chat)
    • Session keys for faster symmetric encryption
    • Other sensitive data
  • Only your private key can decrypt what was encrypted with your public key.

Example:
When your browser connects over HTTPS, the server sends a certificate that includes its public key; your browser uses that public key to securely send over a one-time symmetric key.

2. Verify digital signatures for authenticity

  • You sign something (like software, documents, or website handshakes) with your private key.
  • Anyone can use your public key to check that signature and see:
    • The data wasn’t altered
    • The signature matches your key pair, so it’s really from you

This is how software updates, package managers, and many secure login systems verify that content or messages are genuine.

Where You See Public Keys in Real Life

Even if you’ve never handled a raw key string, you use systems that rely on them every day:

  • HTTPS websites (the padlock icon in your browser)
    • Websites present digital certificates containing their public keys.
  • Secure email (PGP, S/MIME)
    • People publish their public keys so others can send them encrypted emails.
  • Software and app updates
    • Developers sign releases with their private keys; your device checks the signature with their public key.
  • SSH and remote logins
    • You often place your public key on a server so you can log in using your private key instead of a password.

All of this depends on the simple idea: public key = widely known, private key = secret, but they still work together as a pair.

Why Public Keys Matter Today

Public keys are a foundational building block for internet security in 2026, not just a niche math trick.

  • They enable secure communication between strangers over an insecure network like the internet.
  • They support public key infrastructure (PKI) , which underpins SSL/TLS certificates, code-signing, and many identity systems.
  • They make things like end‑to‑end encrypted messaging, VPNs, and many “zero trust” security models possible.

As threats grow and quantum computing is discussed more, there is active research and “latest news” around new public key algorithms (post‑quantum cryptography) that keep the same public/private idea but change the underlying math.

Mini FAQ

Is a public key just a password?
No. A password is something you keep secret and type in, while a public key is meant to be shared openly and only works in combination with its private counterpart.

Can someone hack me if they know my public key?
By design, knowing only the public key should not be enough to derive the private key or decrypt messages, assuming strong algorithms and key lengths are used.

Why not just use one key (symmetric encryption)?
One shared key is fast but hard to distribute safely. Public keys solve the key-sharing problem by letting you publish one key and keep the other private.

Information gathered from public forums or data available on the internet and portrayed here.