README

Overview

This PHP library provides tools for encrypting and decrypting WhatsApp media files (images, audio, video) using the official WhatsApp algorithm. It supports streaming encryption/decryption, MAC validation, and sidecar generation for video integrity.

• Encryption: AES-256-ECB with CBC-like chaining and PKCS#7 padding.
• Decryption: Validates MAC, removes padding, and restores original media.
• Sidecar: Generates chunked MACs for video files (used by WhatsApp for integrity checks).
• Streaming: Works with PSR-7 streams for efficient memory usage.

Features

• Compatible with WhatsApp's official media encryption format
• Handles large files efficiently (streaming, chunked processing)
• Validates MAC for data integrity
• Generates sidecar MACs for video
• Custom exceptions for robust error handling
• Fully tested with PHPUnit and sample files

Installation

Clone the repository and install dependencies:

git clone https://github.com/wizardloong/whatsapp-stream-encryption
cd whatsapp-stream-encryption
composer install

Usage

First, install the package via Composer in your project:

composer require wizardloong/whatsapp-stream-encryption

Then use it in your code:

Encrypting Media

require 'vendor/autoload.php';

use Wizardloong\WhatsAppStreamEncryption\WhatsAppEncryptingStream;
use Wizardloong\WhatsAppStreamEncryption\MediaType;
use GuzzleHttp\Psr7\Utils;

$mediaKey = random_bytes(32); // Or use WhatsApp-provided key
$inputStream = Utils::streamFor(fopen('input.jpg', 'rb'));
$encrypting = new WhatsAppEncryptingStream($inputStream, MediaType::IMAGE, $mediaKey);

$outputStream = fopen('output.encrypted', 'wb');
while (!$encrypting->eof()) {
	fwrite($outputStream, $encrypting->read(8192));
}
fclose($outputStream);

Decrypting Media

require 'vendor/autoload.php';

use Wizardloong\WhatsAppStreamEncryption\WhatsAppDecryptingStream;
use Wizardloong\WhatsAppStreamEncryption\MediaType;
use GuzzleHttp\Psr7\Utils;

$mediaKey = file_get_contents('IMAGE.key');
$encryptedStream = Utils::streamFor(fopen('output.encrypted', 'rb'));
$decrypting = new WhatsAppDecryptingStream($encryptedStream, MediaType::IMAGE, mediaKey);

$outputStream = fopen('output.decrypted.jpg', 'wb');
while (!$decrypting->eof()) {
	fwrite($outputStream, $decrypting->read(8192));
}
fclose($outputStream);

Video Sidecar Generation

require 'vendor/autoload.php';

use Wizardloong\WhatsAppStreamEncryption\WhatsAppEncryptingStream;
use Wizardloong\WhatsAppStreamEncryption\MediaType;
use GuzzleHttp\Psr7\Utils;

$mediaKey = file_get_contents('VIDEO.key');
$inputStream = Utils::streamFor(fopen('input.mp4', 'rb'));
$encrypting = new WhatsAppEncryptingStream($inputStream, MediaType::VIDEO, $mediaKey, true);

$outputStream = fopen('output.encrypted', 'wb');
while (!$encrypting->eof()) {
	fwrite($outputStream, $encrypting->read(16384));
}
fclose($outputStream);

$sidecar = $encrypting->getSidecar();
file_put_contents('output.sidecar', $sidecar);

Running Tests

Tests use PHPUnit and sample files in the samples/ directory.

make test
# or
vendor/bin/phpunit --testdox

Specifications

• Key Expansion: Uses HKDF-SHA256 to derive IV, cipherKey, and macKey from mediaKey and mediaType.
• Encryption: AES-256-ECB, CBC-like chaining (XOR with previous block), PKCS#7 padding.
• MAC: HMAC-SHA256 over IV + ciphertext, first 10 bytes appended as trailer.
• Sidecar (video): HMAC-SHA256 over each 64KB chunk + 16-byte overlap, first 10 bytes per chunk.
• Decryption: Validates MAC, removes PKCS#7 padding, restores original data.
• Exceptions: Throws custom exceptions for encryption/decryption errors.

File Structure

• src/WhatsAppEncryptingStream.php — Streaming encryption implementation
• src/WhatsAppDecryptingStream.php — Streaming decryption implementation
• src/KeyExpander.php — Key derivation logic
• src/MediaType.php — Media type enum
• src/Exceptions/EncryptionException.php — Encryption error class
• src/Exceptions/DecryptionException.php — Decryption error class
• tests/WhatsAppSamplesTest.php — Integration tests
• samples/ — Sample media, keys, and expected outputs

Error Handling

• Throws EncryptionException for encryption failures (OpenSSL, padding, etc.)
• Throws DecryptionException for decryption failures (MAC, padding, etc.)

Notes

• Always use chunked reading/writing for large files to avoid memory issues.
• MediaKey must be 32 bytes (random or WhatsApp-provided).
• Sidecar is only needed for video integrity checks.

License

MIT

Authors

• Victor Miroliubov w.izard@outlook.com

Contributing

Pull requests and issues are welcome!