RAR3-p (Compressed) Hash

What is RAR3-p (Compressed)?

The **RAR3-p (Compressed)** hash format is derived from the proprietary **RAR5** archive format’s password-protection mechanism, which builds upon the **RAR3** (and earlier RAR2) password-hashing schemes. Introduced by WinRAR (developed by Eugene Roshal in the late 1990s), the RAR3-p algorithm was designed as a lightweight, deterministic password-verification mechanism optimized for archival integrity and speed, rather than cryptographic security. Structurally, it combines a **SHA-256-based key derivation** (for the archive header) with a **custom compression-resistant hash** (termed "p") that incorporates the password, archive name, and a **32-bit magic constant** (0x7272 for RAR3-p). The compressed hash is stored as a **64-byte binary blob** (SHA-256 output truncated to 32 bytes) followed by a **16-byte CRC32** of the password+archive metadata, enabling quick verification without decompressing the archive. Its primary use-case was password-protected archive authentication, where efficiency (avoiding full decompression) and compatibility with legacy RAR3 archives were prioritized over cryptographic robustness.

The **RAR3-p (Compressed)** format is vulnerable to cracking due to **three critical design flaws**. First, it lacks **salting**, as the hash derivation relies on a **static magic constant** and **archive metadata** (filename, timestamp) that can be enumerated or guessed, enabling **rainbow table attacks** or **precomputed lookups** for common passwords. Second, the **compression-resistant "p" component** is not a standalone cryptographic primitive but a **deterministic function** of the password concatenated with archive-specific data, making it susceptible to **brute-force optimizations**—modern GPUs and FPGA clusters can hash millions of candidates per second due to the algorithm’s **parallelizable SHA-256 core**. Third, the **32-byte truncated SHA-256** reduces collision resistance, as the **birthday bound** is effectively lowered (requiring ~2³² operations for a collision), and the **CRC32 checksum** provides no cryptographic security, only integrity for the metadata. Additionally, **side-channel attacks** (timing/power analysis) may exploit the algorithm’s **predictable compression behavior** during hash computation, further weakening its resistance to targeted cracking.

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

How to Crack RAR3-p (Compressed)

If you need to recover the plaintext password for a RAR3-p (Compressed) 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.