HMAC-SHA1 (key = $pass) Hash

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

HMAC-SHA1 with a key derived from a password (`HMAC-SHA1(key = $pass)`) is a cryptographic hash function constructed as part of the **Hash-based Message Authentication Code (HMAC)** framework, standardized in RFC 2104 (1997). It combines the **Secure Hash Algorithm 1 (SHA-1)**, a widely adopted 160-bit (512-bit internal state) cryptographic hash function originally designed by the NSA and published in 1995, with a keyed-hash mechanism to produce a fixed-length 160-bit output. The HMAC construction involves a nested XOR-based operation between the hash function’s internal padding constants, the key, and the message, ensuring that even minor changes in the input or key produce drastically different outputs. This format was primarily designed for **message integrity verification and authentication**, where a shared secret (e.g., a password) is used to generate a unique fingerprint for data validation. While HMAC-SHA1 was widely adopted in protocols like IPsec, SSH, and TLS (in early versions), its reliance on SHA-1’s design—particularly its 160-bit output—made it susceptible to evolving cryptographic threats, despite its initial security guarantees.

The vulnerability of HMAC-SHA1 to cracking stems from **SHA-1’s inherent weaknesses**, exacerbated by its use in password-based systems without proper salting or key stretching. SHA-1’s collision resistance was broken in 2005 (via the **SHA-1b** attack), and by 2017, preimage attacks (finding inputs for a given hash) became feasible with optimized hardware. When used as a password hash (`HMAC-SHA1($pass)`), the lack of a **salt** or **work factor** (e.g., iterative hashing like bcrypt or Argon2) allows attackers to precompute hashes via **rainbow tables** or **dictionary attacks**, especially if passwords follow predictable patterns. Additionally, modern **GPU/ASIC optimizations** (e.g., CUDA-accelerated brute-force tools) enable massive parallel cracking of HMAC-SHA1 outputs, reducing the effective security margin to **<2^64** operations for weak passwords. The absence of post-quantum resistance further cements its obsolescence, as quantum algorithms (e.g., Grover’s) could halve the effective key space to ~2^80, rendering it unsuitable for modern security requirements.

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

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

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