HMAC-MD5 (key = $pass) Hash

What is HMAC-MD5 (key = $pass)?

HMAC-MD5 (key = $pass) is a cryptographic hash format derived from the **Keyed-Hash Message Authentication Code (HMAC)** construction, which combines a cryptographic hash function (MD5 in this case) with a secret key to produce a message authentication code. Introduced in RFC 2104 (1997), HMAC was designed to provide data integrity and authenticity by ensuring that a message and its associated key have not been altered. The format typically follows the structure `HMAC-MD5(key, message)`, where the key (often a password or secret string, e.g., `$pass`) is concatenated with the input data through a padding and XOR-based process before being hashed by MD5. This mechanism prevents trivial replay attacks and ensures that even minor changes to the input produce drastically different hash outputs. Historically, HMAC-MD5 was widely deployed in authentication protocols, password storage (e.g., legacy PHP hashing), and lightweight security applications where computational efficiency was prioritized over long-term security. However, its use in password storage—particularly without salting or iteration—became a critical vulnerability due to its deterministic nature and susceptibility to brute-force attacks.

The vulnerability of HMAC-MD5 (key = $pass) stems from fundamental flaws in its design for password hashing. MD5 itself is a **weak cryptographic hash function**, prone to collision attacks and vulnerable to preimage attacks when used without proper salting or key stretching. Without a **salt** (a unique random value per password), identical passwords produce identical hashes, enabling attackers to precompute or reuse hashes in rainbow table attacks. Additionally, MD5’s 128-bit output space is insufficient for modern computational power, allowing for **brute-force cracking via GPU/FPGA clusters** (e.g., via tools like Hashcat) at practical speeds. The absence of **iterative hashing** (e.g., bcrypt, PBKDF2) means the algorithm remains computationally trivial, enabling attackers to test millions of passwords per second. Furthermore, HMAC’s structure—while secure for message authentication—does not inherently resist **timing attacks** or **side-channel exploits**, and its reliance on MD5’s flawed compression function (e.g., the "Pumpkin" collision attack) renders it obsolete for security-sensitive applications. The combination of these factors makes HMAC-MD5 with a plain password key a **catastrophic choice** for modern authentication systems.

Identifying HMAC-MD5 (key = $pass) 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 HMAC-MD5 (key = $pass), security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack HMAC-MD5 (key = $pass)

If you need to recover the plaintext password for a HMAC-MD5 (key = $pass) 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.