MS Office ⇐ 2003 $0/$1, MD5 + RC4, collider #2 Hash

What is MS Office ⇐ 2003 $0/$1, MD5 + RC4, collider #2?

This cryptographic hash format, **"MS Office ≤ 2003 $0/$1, MD5 + RC4, collider #2"**, originates from a legacy password storage scheme used in early versions of Microsoft Office (primarily Outlook and Exchange) prior to 2003, where user credentials were hashed for authentication. The structure involves a two-stage process: first, the plaintext password is hashed using **MD5**, producing a 128-bit digest. The resulting hash is then prefixed with a **$0** (for MD5) or **$1** (for legacy SHA-1 variants in some cases), followed by the actual hash bytes. In the second stage, the hashed value is fed into an **RC4 keystream generator** to derive a symmetric key for subsequent encryption operations, such as S/MIME or RPC authentication. This hybrid scheme was designed to maintain backward compatibility with older systems while leveraging MD5’s widespread availability, though it was never intended for secure password storage—rather, it served as a lightweight, non-standardized mechanism for internal Microsoft applications.

The vulnerability of this format stems from fundamental cryptographic flaws compounded by implementation oversights. **MD5 is inherently collision-prone**, with known preimage and second-preimage attacks, while its 128-bit output space is easily exhausted via brute-force or rainbow table attacks, especially when combined with weak password policies. The absence of a **salt** (or a per-user pepper) eliminates uniqueness, allowing attackers to precompute hashes for common passwords (e.g., via rainbow tables). The **RC4 component**, though not directly vulnerable on its own, introduces entropy only after the MD5 stage, meaning the core weakness remains the MD5 hash’s predictability. Additionally, modern **GPU/ASIC acceleration** (e.g., via tools like Hashcat) can crack MD5 hashes at rates exceeding **100+ GH/s**, rendering the scheme impractical for security. The **"collider #2"** reference likely alludes to a specific attack vector exploiting MD5’s deterministic nature, enabling targeted collisions or brute-force recovery of plaintexts from hashed credentials.

Identifying MS Office ⇐ 2003 $0/$1, MD5 + RC4, collider #2 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 MS Office ⇐ 2003 $0/$1, MD5 + RC4, collider #2, security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack MS Office ⇐ 2003 $0/$1, MD5 + RC4, collider #2

If you need to recover the plaintext password for a MS Office ⇐ 2003 $0/$1, MD5 + RC4, collider #2 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.