De-hashing

In short: De-hashing means determining the original value of a hash. A real reversal does not exist.

In more detail: A hash function is a one-way street. You can only guess, for example by brute force, dictionary or rainbow table, and check whether the hash matches.

In Depth

Methods

• Brute force: try all combinations.
• Dictionary: common passwords and variants.
• Rainbow tables: precomputed hashes (ineffective against salt).

Protection for passwords

Slow methods with salt and pepper: bcrypt, scrypt, Argon2. Never fast hashes (MD5, SHA-1) for passwords. See hashing, decrypting.

See also: Hashing, Decrypting, Encryption