Rainbow Table
A precomputed table for caching the outputs of a cryptographic hash function
A rainbow table is a large, precomputed table designed to cache the output of cryptographic hash functions to decrypt hashed passwords into plaintext. Rainbow tables were invented by IT expert Philippe Oechslin, who published a paper on his work in 2003.
For security reasons organizations have, for several years, typically stored users’ passwords using hashes. Hashing algorithms disguise passwords and make them unviewable to anyone without inverting the hash function. This can technically be achieved via brute-force attacks, but as the set of possible password outcomes grows, it becomes more and more infeasible to use this method.
Rainbow tables greatly reduce the complexity in cracking large numbers of passwords through a pre-generated data set of password hashes.
Vast numbers of hashed passwords can be run through this data set and, following several stages of reduction by which hashes are split into smaller components, computed and linked to words and letters to reveal whole passwords in plaintext.