Introduction to PGP Encryption

What is PGP Encryption?

Pretty Good Privacy (PGP) is an encryption program that provides cryptographic privacy and authentication for data communication. Developed by Phil Zimmermann in 1991, PGP has become the global standard for encrypted communications.

At its core, PGP enables you to:

• Encrypt messages so only intended recipients can read them
• Digitally sign messages to verify your identity
• Verify the authenticity of received messages
• Ensure message integrity (detect if content has been altered)

Why Use PGP Encryption?

In today's digital landscape, unencrypted emails are comparable to sending postcards through the mail — anyone handling them can read their contents. PGP effectively puts your message in a secure, sealed envelope that only the recipient can open.

Here are key reasons to use PGP encryption:

Privacy Protection

Standard email is inherently insecure. Messages typically travel through multiple servers and networks before reaching their destination, creating numerous points where they could be intercepted and read. PGP ensures that even if your message is intercepted, its contents remain unreadable to anyone except the intended recipient.

Authentication

Through digital signatures, PGP verifies the sender's identity. This prevents email spoofing and ensures recipients can trust that messages truly came from you.

Integrity

PGP detects if a message has been tampered with during transmission. Even minor alterations to the encrypted message will be flagged when the recipient attempts to decrypt it.

How PGP Works: A Simple Explanation

PGP uses a combination of two encryption methods:

Symmetric Encryption

In symmetric encryption, the same key is used to both encrypt and decrypt data. Think of it like a physical key to a door — the same key locks and unlocks it. This method is very fast and efficient for encrypting large amounts of data.

Asymmetric Encryption (Public Key Cryptography)

In asymmetric encryption, two mathematically related keys are used: a public key and a private key.

• Public key: Shared openly with anyone, used to encrypt messages to you
• Private key: Kept secret, used to decrypt messages sent to you

What makes this system powerful is that content encrypted with your public key can only be decrypted with your private key. This creates a one-way security system that allows anyone to send you encrypted messages without having to securely share a password first.

PGP in Action: The Encryption Process

When you send a PGP-encrypted email, here's what happens:

1. Create message: You write your email message
2. Generate session key: PGP creates a random one-time symmetric key (session key)
3. Encrypt message: Your message is encrypted using this session key
4. Encrypt session key: The session key itself is encrypted using the recipient's public key
5. Combine and send: Both the encrypted message and the encrypted session key are sent to the recipient

When the recipient receives your encrypted email:

1. Decrypt session key: They use their private key to decrypt the session key
2. Decrypt message: They use the session key to decrypt the actual message
3. Read message: They can now read the original message contents

      
        
# Encrypt a file for a recipient
gpg --encrypt --recipient [email protected] confidential_document.txt

# The result will be a new file: confidential_document.txt.gpg

      
    

GPG vs. PGP: What's the Difference?

You'll often see the terms PGP and GPG used interchangeably, which can be confusing. Here's a quick explanation of the difference:

• PGP (Pretty Good Privacy) is the original encryption program created by Phil Zimmermann in 1991. It's now owned by Symantec and is available as a commercial product.
• GPG (GNU Privacy Guard or GnuPG) is a free, open-source implementation of the OpenPGP standard (the standardized version of PGP). It provides the same encryption functionality but is freely available and maintained by the Free Software Foundation.

For practical purposes, both achieve the same core functionality of securing communications through encryption. In this Academy, we'll generally use "PGP" to refer to the encryption standard and concept, but the actual implementations we'll work with are typically GPG-based.

Getting Started with PGP

The easiest way to start using PGP encryption is with Secure Mail Client, which handles all the technical complexities for you while maintaining the highest security standards.

In the next module, we'll explore the concept of Public Key Infrastructure in more detail, which is the foundation of how PGP encryption works.