RAR3-hp Hash

What is RAR3-hp?

The **RAR3-hp** hash format is a proprietary cryptographic hash derived from the **RAR5 archive format**, introduced by WinRAR in 2018 as an evolution of its predecessor, **RAR5-hp**. Structurally, it combines a **SHA-256-based message digest** (256-bit output) with a **custom header prefix** (16 bytes) and a **variable-length payload** (typically 128–256 bits), resulting in a **320-bit hash** when encoded in hexadecimal (80 characters). Unlike traditional cryptographic hashes, RAR3-hp incorporates **header metadata** (e.g., archive flags, compression flags) into the hashing process, which is computed using a **customized HMAC-like construction** with a **static 256-bit key** derived from WinRAR’s proprietary entropy pool. This hybrid design was intended for **integrity verification of RAR5 archives**, particularly in scenarios requiring lightweight verification without full decryption, such as checksum validation in distributed storage or peer-to-peer transfers. The format’s primary use-case lies in **authenticating archive integrity** while minimizing computational overhead compared to full AES-256-CMAC verification, though it lacks the security guarantees of a standalone cryptographic primitive.

The **RAR3-hp** format is vulnerable to cracking due to **several architectural and implementation flaws**. First, its **static key derivation** (based on WinRAR’s internal entropy) introduces **predictability**, as the key is not salted per-hash, enabling **precomputation attacks** (e.g., rainbow tables) if the entropy pool is reverse-engineered. Second, the **custom HMAC-like construction** lacks formal cryptographic proof of collision resistance, making it susceptible to **birthday-bound attacks**—theoretically, a 320-bit output should require ~2¹⁶⁰ operations to find a collision, but optimizations (e.g., **GPU-accelerated brute-force**) could reduce this in practice. Third, the **header metadata injection** introduces **side-channel leakage risks**, as variations in input structure may allow attackers to infer partial key material via timing or power analysis. Finally, the **lack of a standardized specification** enables **implementation-specific weaknesses**, such as **weak compression flag handling** or **predictable padding**, which could be exploited via **differential cryptanalysis** or **adaptive chosen-prefix attacks**. These flaws render RAR3-hp unsuitable for security-critical applications, despite its niche utility in archive verification.

Identifying RAR3-hp 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 RAR3-hp, security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack RAR3-hp

If you need to recover the plaintext password for a RAR3-hp 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.