How PDF Encryption Works | Rune

PDF protection isn't just a lock on the door—it's mathematical encryption that scrambles content. Here's how it works.

What is Encryption?

Encryption transforms readable content into unreadable scrambled data. Only the correct password (decryption key) can reverse the process.

PDF Encryption Basics

Symmetric Encryption

PDFs use symmetric encryption: the same password encrypts and decrypts.

Original PDF → Encryption (password) → Encrypted PDF
Encrypted PDF → Decryption (password) → Original PDF

The Algorithm

Modern PDFs use AES (Advanced Encryption Standard):

• Government-approved security
• 128-bit or 256-bit keys
• Computationally secure

How It Works Step by Step

Encryption (Protecting)

1. You provide a password.
2. The password is processed into an encryption key.
3. Document content is scrambled using this key.
4. Encrypted file is created.

Decryption (Opening)

1. You enter the password.
2. The password is processed into the same key.
3. Key decrypts the scrambled content.
4. Original document appears.

Security Strength

AES Version	Key Size	Security Level
AES-128	128 bits	Strong
AES-256	256 bits	Very Strong

Both are effectively unbreakable with good passwords.

What Gets Encrypted?

• All text content
• Images and graphics
• Document metadata (optionally)
• Embedded files
• Form data

What Doesn't Get Encrypted?

• File existence (still visible in file system)
• File size (approximate content size visible)
• PDF marker (identified as PDF file)

Password Importance

Encryption is only as strong as the password. A weak password undermines strong encryption.

Password	Time to Crack
6 characters, letters only	Minutes
8 characters, mixed	Hours to Days
12 characters, complex	Years
16+ characters, complex	Centuries+

Using Rune's Encryption

Rune's Protect PDF uses industry-standard encryption. Your strong password becomes the key to mathematical protection.

Conclusion

PDF encryption is proven technology. Understanding it helps you appreciate why strong passwords matter for Rune's Protect PDF.