Microsoft Office ≤ 2003 (MD5+RC4) Hash

What is Microsoft Office ≤ 2003 (MD5+RC4)?

The cryptographic hash format "Microsoft Office ≤ 2003 (MD5+RC4)" represents a legacy authentication scheme embedded in older versions of Microsoft Office (pre-2004) for securing document templates and macros via digital signatures. This hybrid mechanism combines **MD5 (Message-Digest Algorithm 5)** as the hash function for generating a fixed-length 128-bit (16-byte) fingerprint of the document’s contents, while **RC4 (Rivest Cipher 4)**, a stream cipher, encrypts the hash with a user-provided password before storage. The structure involves three core components: the document’s hash (derived via MD5), the RC4-encrypted hash, and a timestamp. This format was primarily designed to verify document integrity and authenticate macro authorship, ensuring that tampered templates or unauthorized modifications could be detected. However, its deployment was limited to internal Office workflows, particularly in legacy enterprise environments where compatibility with older systems was critical.

The vulnerability of this scheme stems from fundamental cryptographic flaws exacerbated by implementation oversights. **MD5’s collision resistance is severely compromised**, as demonstrated by practical attacks (e.g., SHA-1/MD5 preimage attacks) that enable forgery of document hashes without knowledge of the original content. The absence of **salting** in the RC4 encryption process renders it susceptible to **rainbow table attacks**, as identical passwords produce identical encrypted hashes, allowing offline brute-force decryption. Additionally, **RC4’s inherent weaknesses**—such as predictable keystream patterns and side-channel vulnerabilities—were further exploited via GPU-accelerated cracking tools (e.g., Hashcat) targeting the stream cipher’s linear feedback shift register (LFSR). The lack of iteration limits, combined with the **computational efficiency of GPU clusters**, reduced the time complexity of password recovery to near-linear, rendering the scheme effectively broken for password-based authentication. Even if the document hash remains intact, the RC4 component’s predictability enables full key recovery, undermining the entire integrity-verification mechanism.

Identifying Microsoft Office ≤ 2003 (MD5+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 (MD5+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 (MD5+RC4)

If you need to recover the plaintext password for a Microsoft Office ≤ 2003 (MD5+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.