Pure PHP MD5 Hash Implementation

Discover a step-by-step guide to implementing the MD5 hashing algorithm in pure PHP. Perfect for developers seeking to understand MD5 internals

PHP Code Editor

<?php
function md5_custom($input) {
// Initialize MD5 constants
$s = [7, 12, 17, 22, 5, 9, 14, 20, 4, 11, 16, 23, 6, 10, 15, 21];
$K = array_map(function ($i) {
return floor(abs(sin($i + 1)) * (2 ** 32));
}, range(0, 63));
// Pre-processing
$input = array_map("ord", str_split($input)); // Convert input string to array of ASCII values
$length = count($input) * 8; // Message length in bits
$input[] = 0x80; // Append 1 bit followed by zeros
while ((count($input) * 8) % 512 !== 448) {
$input[] = 0x00; // Pad with zeros until length is congruent to 448 mod 512
}
// Append the original length as a 64-bit number (little-endian)
for ($i = 0; $i < 8; $i++) {
$input[] = ($length >> ($i * 8)) & 0xFF;
}
// Process each 512-bit chunk
$chunks = array_chunk($input, 64);
 
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PHP Version

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Description

This implementation provides a step-by-step recreation of the MD5 hashing algorithm in pure PHP, without relying on built-in functions like md5(). It helps developers understand the internal workings of MD5, including its padding, processing, and bitwise operations.

Key Features of the Code

  1. Custom Implementation:
    A complete implementation of the MD5 algorithm written from scratch in PHP.

  2. Bitwise Operations:
    Uses low-level bitwise operations to mimic the MD5 algorithm’s functionality, such as logical AND, OR, XOR, and NOT.

  3. Padding and Chunking:
    Handles input padding and chunking according to MD5’s specification.

  4. Mathematical Constants:
    Uses predefined constants derived from the sine function to implement the MD5 transformations.

MD5 Algorithm Breakdown
1. Initialization:

The algorithm begins by initializing four 32-bit variables (A, B, C, D) with predefined constants

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