md4($pass.$salt) Hash

What is md4($pass.$salt)?

The cryptographic hash format `md4($pass.$salt)` originates from the MD4 (Message-Digest algorithm 4) hash function, designed by Ronald L. Rivest in 1990 as part of the MD family of hashing algorithms. MD4 operates as a 128-bit hash function, processing input data through three distinct compression rounds—each involving bitwise operations (AND, OR, XOR), modular addition, and left-rotational shifts—to produce a fixed-length digest. The format `$pass.$salt` denotes a concatenation of a user-provided password (`$pass`) and a unique salt (`$salt`) before hashing, a technique intended to mitigate rainbow table attacks by ensuring each password requires a unique hash. Historically, MD4 was widely adopted in early web frameworks (e.g., PHP’s `md5()` predecessor) and legacy systems for password storage due to its simplicity and moderate performance, though it was quickly superseded by stronger algorithms like SHA-1 and SHA-2. Its primary use-case was password hashing, though its cryptographic security was never intended for digital signatures or data integrity beyond basic checksums.

The `md4($pass.$salt)` format is critically vulnerable to cracking due to MD4’s inherent design flaws and practical implementation weaknesses. MD4 suffers from severe collision vulnerabilities—demonstrated in 1996—where distinct inputs can produce identical hashes, rendering it unsuitable for cryptographic purposes. Even with salting, MD4’s compression function lacks sufficient avalanche effect, allowing attackers to exploit patterns in precomputed tables or brute-force attacks. Modern GPUs and FPGAs can evaluate millions of MD4 hashes per second, enabling efficient rainbow table attacks or brute-force cracking of hashed passwords, especially when salts are weak or reused. Additionally, MD4’s 128-bit output space is insufficient against contemporary computational power, and its reliance on concatenation (rather than proper keyed hashing) fails to provide semantic security, as the salt’s role is undermined by the algorithm’s predictable behavior. These flaws render `md4($pass.$salt)` catastrophically insecure for password storage, necessitating migration to modern keyed hashing schemes like bcrypt, Argon2, or PBKDF2.

Identifying md4($pass.$salt) Hashes

Identifying a hash blindly is often difficult because multiple algorithms can output strings of the exact same length. For example, a standard 32-character hexadecimal string could be MD5, NTLM, MD4, or LM. To definitively identify md4($pass.$salt), security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack md4($pass.$salt)

If you need to recover the plaintext password for a md4($pass.$salt) hash during a penetration test or forensics investigation, you must supply the correct module ID to your cracking software. Use the exact commands provided at the top of this page to target the hash successfully.