HMAC-SHA1 (key = $salt) Hash

What is HMAC-SHA1 (key = $salt)?

HMAC-SHA1 with a salt (key = $salt) is a cryptographic construction derived from the **Keyed-Hash Message Authentication Code (HMAC)** framework, standardized in RFC 2104, combined with the **SHA-1** hash function (FIPS 180-1). The algorithm was designed to provide message integrity and authentication by leveraging a secret key (here, the salt) to produce a fixed-length 160-bit (20-byte) hash output. Structurally, HMAC-SHA1 follows a nested key-derivation process: the key is first padded with a constant (0x36) and XORed with an inner hash block, processed through SHA-1, then XORed with a constant (0x5C), and finally hashed again. This format is primarily used in password storage (e.g., PHP’s `password_hash()` with PASSWORD_DEFAULT) and digital signatures, where the salt mitigates precomputed attack vectors like rainbow tables by ensuring uniqueness per credential. However, its reliance on SHA-1—now cryptographically broken due to collision vulnerabilities—compromises its long-term security, despite the salt’s role in preventing offline brute-force attacks.

HMAC-SHA1 is vulnerable to cracking due to SHA-1’s inherent weaknesses, the salt’s limited entropy, and hardware-accelerated optimization. SHA-1’s collision resistance was shattered in 2017 (e.g., SHA-1DREAM), enabling adversaries to forge hashes with practical computational effort, undermining HMAC’s integrity guarantees. While the salt (key = $salt) defends against rainbow tables, it does not mitigate **graceful degradation attacks** or **length-extension vulnerabilities** in HMAC, where prepended data can be hashed without knowing the secret key. Moreover, modern GPUs/ASICs (e.g., via OpenCL or FPGA implementations) can perform **hashcat-style brute-force attacks** at terahashes-per-second, rendering HMAC-SHA1 impractical for high-security contexts. The salt’s randomness must also be sufficiently long (e.g., 128+ bits) to avoid **birthday-bound exhaustion**, but even then, the algorithm’s output size (160 bits) is insufficient for modern cryptographic standards (e.g., NIST’s 2024 recommendations favor 256-bit hashes).

Identifying HMAC-SHA1 (key = $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 HMAC-SHA1 (key = $salt), security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack HMAC-SHA1 (key = $salt)

If you need to recover the plaintext password for a HMAC-SHA1 (key = $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.