What is a rainbow table?
A rainbow table is a precomputed structure that maps hashes back to the passwords that produced them, trading storage for speed. Against unsalted hashes it turns cracking into a lookup. Salting defeats it entirely, because every account's hash would need its own table.
- Topic
- Attacks
- Reading time
- 1 min
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Why they matter less than they used to
Two things reduced their relevance. Salting became standard, which makes precomputation useless. And GPU cracking became so fast that computing hashes on demand is often cheaper than storing and searching terabytes of tables. Rainbow tables remain a good illustration of why salt exists.
Sources
These primary references support the terminology and current security guidance used in this definition.
OWASPPassword Storage Cheat SheetPractical guidance for salts, peppers, PBKDF2, Argon2id, and password hashes.CISASecure Our WorldPublic guidance for recognizing phishing and protecting high-value accounts.NISTComputer Security Resource Center glossaryCanonical terminology used across US computer security guidance.
