Cisco Type 8 Hash

What is Cisco Type 8?

Cisco Type 8, also known as the **MD5-based Cisco password hash**, emerged as a proprietary cryptographic format in the late 1990s to secure user authentication within Cisco IOS and later IOS-XE systems. Structurally, it encodes passwords using a modified MD5 hashing process where the plaintext password is first concatenated with a **static salt** (the string `"$1$"` followed by a 12-character random salt derived from the system’s uptime), then hashed in two rounds: first with MD5, and second with a **1000-round iteration count** (though this was later reduced to 2500 in some implementations). The final output is a 32-byte (256-bit) hexadecimal string, typically stored in configuration files (e.g., `enable` or `username` passwords) with a prefix like `$1$$`. This format was designed for backward compatibility with legacy systems but lacked formal cryptographic scrutiny, relying instead on Cisco’s internal security assumptions. Its primary use-case was password storage in network devices, where performance and simplicity outweighed modern security best practices.

The vulnerability of Cisco Type 8 stems from its **predictable salt structure**, **weak iteration count**, and **MD5’s inherent collision susceptibility**. The static salt prefix (`$1$`) and limited salt entropy (12 characters) enable **rainbow table attacks**, where precomputed hashes of common passwords can be matched against stored hashes. Even with iterations, MD5’s 128-bit output is vulnerable to **birthday attack optimizations**, particularly when combined with GPU/FPGA acceleration (e.g., via tools like Hashcat). The reduced iteration count (2500 rounds) is insufficient to mitigate brute-force attacks, as modern hardware can evaluate millions of hashes per second. Additionally, the lack of **key stretching** or **salting variability** renders it susceptible to **offline dictionary attacks**, where attackers exploit the deterministic nature of the hash function to reverse-engineer passwords efficiently.

Identifying Cisco Type 8 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 8, security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack Cisco Type 8

If you need to recover the plaintext password for a Cisco Type 8 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.