sha256(sha256($pass).sha256($pass)) Hash

What is sha256(sha256($pass).sha256($pass))?

The cryptographic hash format `sha256(sha256($pass).sha256($pass))` is a nested hashing scheme derived from the SHA-256 algorithm, a member of the SHA-2 family standardized by NIST (FIPS 180-4). This construction, often referred to as a *double-hash* or *SHA-256 concatenation*, was historically employed in password storage to mitigate early cryptanalysis techniques by introducing computational overhead and structural complexity. The mechanism operates by first concatenating two SHA-256 hashes of the input password (e.g., `$pass`), then hashing the resulting 64-byte string (128 hex characters) with another SHA-256 iteration. While not explicitly designed for password hashing, its use in legacy systems stemmed from the belief that chaining hashes would increase resistance to brute-force attacks by obscuring intermediate states. However, this approach lacks formal cryptographic justification and deviates from modern best practices like PBKDF2, bcrypt, or Argon2, which explicitly incorporate salting, work factors, and adaptive resistance to hardware acceleration.

This format is fundamentally vulnerable to cracking due to its susceptibility to **precomputed rainbow table attacks** (lacking a salt) and **optimized brute-force techniques** enabled by its deterministic structure. The concatenation of two SHA-256 outputs—without salting or peppering—reduces the hash’s uniqueness, as identical passwords produce identical intermediate states, enabling offline dictionary attacks. Furthermore, the absence of a work factor (e.g., iterative hashing or CPU-bound operations) allows modern GPU/ASIC clusters to evaluate millions of hashes per second, rendering the scheme impractical for real-world security. Collision resistance is also compromised, as SHA-256’s 256-bit output space can be exploited with advanced algorithms (e.g., birthday paradox attacks) when combined with weak input diversity. Additionally, the format’s reliance on simple string concatenation (rather than cryptographic key derivation) fails to account for timing attacks or side-channel vulnerabilities, making it obsolete against contemporary cryptanalytic tools.

Identifying sha256(sha256($pass).sha256($pass)) 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 sha256(sha256($pass).sha256($pass)), security researchers analyze the hash against a strict regular expression (regex) signature (shown above) to find structural matches.

How to Crack sha256(sha256($pass).sha256($pass))

If you need to recover the plaintext password for a sha256(sha256($pass).sha256($pass)) 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.