WhatsApp Media Decryption

Introduction to WhatsApp Media Decryption #

This documentation provides a comprehensive guide on how to decrypt WhatsApp media files (images, audio, and video) using the media URL and media key provided in WhatsApp’s API payloads. WhatsApp encrypts all media files for security and privacy purposes, and this guide explains how to properly decrypt these files for legitimate applications.

Please ensure you comply with WhatsApp’s Terms of Service and applicable laws when implementing this decryption functionality. This documentation is provided for educational and legitimate development purposes only.

How WhatsApp Media Encryption Works #

WhatsApp uses AES-256-CBC encryption for media files with the following workflow:

1. Each media file has a unique mediaKey generated when the file is sent
2. The mediaKey is used as input to a key derivation function (HKDF) to create encryption keys
3. The derived keys are used for AES-256-CBC encryption/decryption
4. The encrypted media is stored on WhatsApp’s servers and accessed via a URL
5. To decrypt, you need both the media URL and the mediaKey

Common Decryption Functions #

All media types (images, audio, videos) share these common functions for decryption:

HKDF Key Derivation Function #

The HKDF (HMAC-based Key Derivation Function) is used to derive cryptographic keys from the mediaKey.

HKDF Key Derivation Function #

The HKDF (HMAC-based Key Derivation Function) is used to derive cryptographic keys from the mediaKey.

Code Snippets and Usage Examples in Github #