Cisco Type 7 Hash

What is Cisco Type 7?

Cisco Type 7 is a proprietary cryptographic hash function developed by Cisco Systems in the late 1990s as part of its legacy authentication and encryption framework, primarily for securing router and switch configurations via the Cisco Secure ID (CSID) authentication protocol. Structurally, it operates as a keyed-hash message authentication code (HMAC)-like mechanism, combining a 16-byte (128-bit) secret key with a variable-length input string (typically a password or passphrase) to produce a 16-byte (128-bit) hash output. The algorithm employs a custom iterative compression function with multiple rounds of bitwise operations, including XOR, modular addition, and nonlinear transformations, designed to resist early brute-force attacks. Unlike standard HMAC-SHA or MD5, Cisco Type 7 lacks formal cryptographic scrutiny and was intended for internal use in Cisco’s proprietary hardware, where performance and compatibility with legacy systems took precedence over modern security standards. Its primary use-case was password storage and authentication within Cisco IOS configurations, though it was later deprecated in favor of stronger alternatives like SHA-256 with salt.

The vulnerability of Cisco Type 7 stems from its outdated design choices and computational inefficiencies that render it susceptible to modern cryptanalysis. The absence of a salt or pepper mechanism means password hashes derived from identical inputs (e.g., default credentials) produce identical outputs, enabling efficient offline dictionary attacks. Its 128-bit output space is trivial to exhaust via GPU-accelerated brute-force tools like Hashcat, particularly when combined with weak password policies (e.g., short, predictable strings). Additionally, the algorithm’s fixed-key structure allows for rainbow table precomputation, further accelerating cracking. The lack of collision resistance—due to its iterative but non-cryptographically optimized compression—also enables practical birthday attack scenarios. Finally, Cisco Type 7’s reliance on legacy hardware optimizations (e.g., 32-bit word operations) makes it vulnerable to timing attacks and side-channel exploits, as modern CPUs and GPUs can evaluate billions of hashes per second, rendering it effectively broken for any security-sensitive application.

Identifying Cisco Type 7 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 Cisco Type 7, security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack Cisco Type 7

If you need to recover the plaintext password for a Cisco Type 7 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.