Microsoft Office ≤ 2003 (SHA1+RC4) Hash

What is Microsoft Office ≤ 2003 (SHA1+RC4)?

The **Microsoft Office ≤ 2003 (SHA1+RC4)** hash format was introduced as part of the legacy password storage mechanism used in early versions of Microsoft Office applications (primarily Office 2000, XP, and 2003) for securing document permissions via encrypted XML-based digital signatures. This scheme combined **SHA-1** for hashing and **RC4** (a stream cipher) for encryption, where the user’s password was first hashed with SHA-1, then the resulting 160-bit hash was concatenated with a static salt (the username or a fixed string) before being encrypted with RC4. The encrypted output was stored in the Office document’s XML metadata, enabling authentication via a challenge-response protocol. While designed to prevent plaintext password storage, this format was never intended for high-security applications—its primary use-case was lightweight permission control within proprietary file formats, where security was secondary to interoperability and backward compatibility.

The vulnerability of this format stems from fundamental cryptographic flaws exacerbated by implementation weaknesses. SHA-1, though collision-resistant at design, is now considered broken for security due to its susceptibility to preimage attacks (e.g., SHA-1 hashing collisions have been demonstrated in practice), while RC4’s stream cipher properties are vulnerable to timing attacks and key-recovery exploits when used with weak keys (e.g., short or predictable salts). The absence of a dynamic salt (e.g., per-password or per-document) allows attackers to precompute or brute-force hashes efficiently, particularly when combined with GPU-accelerated SHA-1 cracking tools (e.g., Hashcat’s `sha1` mode). Additionally, the RC4 encryption lacks proper padding or integrity checks, enabling chosen-plaintext attacks if an attacker can manipulate the encrypted payload. Modern hardware (CPUs/GPUs) further accelerates brute-force efforts, rendering this scheme susceptible to offline cracking within hours or days for weak passwords, despite the SHA-1’s 160-bit output space.

Identifying Microsoft Office ≤ 2003 (SHA1+RC4) 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 Microsoft Office ≤ 2003 (SHA1+RC4), security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack Microsoft Office ≤ 2003 (SHA1+RC4)

If you need to recover the plaintext password for a Microsoft Office ≤ 2003 (SHA1+RC4) 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.