PGP Essentials: A Practical Guide

PGP (Pretty Good Privacy) helps you protect your messages online. It uses long-established cryptographic methods to ensure only the intended recipient can read your message, and it lets you verify that a message truly came from the sender. Built on open standards, PGP is a reliable and widely trusted tool for securing your communications.

Why Use PGP?

PGP prevents others from reading your private conversations and stops attackers from pretending to be someone else. Its principles and technologies have been battle-tested over decades, providing robust security for email, files, and other communications.

The Basics

PGP relies on a pair of keys:

  • Public Key: Share this with anyone who needs to send you an encrypted message.
  • Private Key: Keep this secret. It decrypts messages meant for you and creates digital signatures to prove you wrote a message.

Imagine three people:

  • Alice wants to send secure messages.
  • Bob wants to receive them.
  • Eve tries to intercept and read them without permission.
  1. Bob sends Alice his public key.
  2. Alice uses that public key to encrypt her message.
  3. Bob uses his private key to decrypt it. Eve can’t read it because she doesn’t have Bob’s private key.

Encryption and Signing

  • Encryption: Scrambles a message so only the intended recipient can read it.
  • Decryption: Returns the scrambled message to its original form using the private key.
  • Signing: A digital “stamp” created with your private key that proves a message really came from you.

When Alice signs a message, Bob uses her public key to verify the signature. If it checks out, he knows Alice sent it and that no one altered it.

Algorithms and Key Sizes

PGP uses proven mathematical algorithms like RSA and ECC, which are based on open standards. These algorithms have stood the test of time, offering reliable security. Larger keys are harder to break but slower to use. Common choices include:

  • RSA 2048-bit: Widely supported, generally secure.
  • ECC (Ed25519, ECDH): Smaller keys with strong security and faster performance.

Key Management

  • Expiration: Keys can expire after a set time to reduce long-term risk.
  • Revocation: If you lose control of your private key, you can revoke it, telling others not to trust it anymore.

Building Trust: The Web of Trust

There’s no central authority in PGP. Instead, people sign each other’s public keys if they trust them. Over time, these links create a “web” that helps users decide whom to trust. This decentralized approach, based on open standards, enhances security and flexibility.

Getting Started

  1. Pick a Tool: GnuPG (GPG) is a popular, free choice included with most Linux distributions. GPG4Win is a user-friendly option for Windows, bundling GnuPG with graphical tools to make key management and encryption easier.
  2. Generate a Key Pair: Create a public and private key.
  3. Share Your Public Key: Give it to people who need to send you encrypted messages.
  4. Keep Your Private Key Safe: Use a strong passphrase and back it up securely.
  5. Practice: Encrypt, decrypt, sign, and verify messages with people you trust.

Conclusion

PGP is a powerful and time-tested way to protect your communications. Built on open standards and proven through years of use, it ensures your conversations remain secure and authentic in a world full of digital threats. By understanding public and private keys, encryption, and signing, you can confidently safeguard your digital interactions.