MD4 vs MD5: Understanding Hash Function Collisions and Their Impact on Security

Introduction

Cryptographic hash functions are essential tools in modern computing, widely used for data integrity, password hashing, digital signatures, and more. Among the earliest hash functions, MD4 and MD5 were designed to securely map data of arbitrary length to fixed-length output. However, both MD4 and MD5 have been found to be vulnerable to a fundamental weakness in cryptography: collisions.

A collision occurs when two different inputs result in the same hash output. This flaw undermines the primary purpose of hash functions — to uniquely represent input data. The discovery of such vulnerabilities in MD4 and MD5 has led to their deprecation in favor of more secure hash functions. This article will delve into the specifics of how collisions in MD4 and MD5 occur, the impact these collisions have on security, and why MD4 is more susceptible to collisions than MD5. Additionally, we will explore the history and evolution of these hash functions, their cryptographic weaknesses, and the reasons they are no longer considered secure for cryptographic applications.

The Basics of MD4 and MD5

Before discussing the security implications of collisions, it’s important to understand what MD4 and MD5 are and how they…