NTHash(FreeBSD Variant) Hash

What is NTHash(FreeBSD Variant)?

The **NTHash (FreeBSD Variant)** is a cryptographic hash format derived from the traditional Unix password hashing scheme, originally designed for compatibility with the NetBSD password database format (`/etc/pw.db`). Unlike the classic Unix DES-based hashing, FreeBSD’s NTHash variant employs a modified **Blowfish-based** algorithm (introduced in OpenBSD’s `crypt(3)` with the `-n` flag) to mitigate weaknesses in traditional DES hashing. Structurally, it consists of a 16-character hexadecimal string prefixed with `$2a$` (indicating Blowfish with a 256-bit salt) or `$2y$` (a later variant with stronger parameters), followed by the salt (14 characters) and the hashed password (31 characters). The format was introduced in FreeBSD 5.0 (2003) to replace the insecure MD5-based hashes used in older systems, offering a balance between security and backward compatibility. Its primary use-case remains password storage in `/etc/master.passwd`, though it is now considered obsolete due to its susceptibility to brute-force attacks.

The FreeBSD NTHash variant is vulnerable to cracking primarily due to its **predictable salt structure** (128-bit salt truncated to 14 characters) and reliance on **Blowfish in CBC mode with a fixed iteration count (256 rounds by default)**, which, while stronger than DES, remains vulnerable to GPU/ASIC acceleration via tools like **Hashcat** or **John the Ripper**. The lack of a **dynamic cost factor** (unlike modern Argon2 or bcrypt) allows attackers to optimize cracking speed by leveraging parallelized hardware (e.g., FPGA/ASIC-based password crackers). Additionally, the **fixed 22-character output length** (after base64 encoding) enables **rainbow table precomputation**, and the absence of **salting entropy expansion** (e.g., per-password salts) reduces resistance to offline brute-force attempts. While stronger than DES or MD5, its design predates modern cryptographic best practices, making it unsuitable for contemporary security requirements.

Identifying NTHash(FreeBSD Variant) 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 NTHash(FreeBSD Variant), security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack NTHash(FreeBSD Variant)

If you need to recover the plaintext password for a NTHash(FreeBSD Variant) 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.