彩虹表： 

彩虹表（Rainbow Tables）就是一个庞大的、针对各种可能的字母组合预先计算好的哈希值的集合，常用来破解md5。

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RainbowCrack

Introduction

RainbowCrack is a general propose implementation of Philippe Oechslin's . It crack hashes with rainbow tables.

RainbowCrack uses time-memory tradeoff algorithm to crack hashes. It differs from brute force hash crackers.

A brute force hash cracker generate all possible plaintexts and compute the corresponding hashes on the fly, then compare the hashes with the hash to be cracked. Once a match is found, the plaintext is found. If all possible plaintexts are tested and no match is found, the plaintext is not found. With this type of hash cracking, all intermediate computation results are discarded.

A time-memory tradeoff hash cracker need a pre-computation stage, at the time all plaintext/hash pairs within the selected hash algorithm, charset, plaintext length are computed and results are stored in files called rainbow table. It is time consuming to do this kind of computation. But once the one time pre-computation is finished, hashes stored in the table can be cracked with much better performance than a brute force cracker.

In this project, we focus on the development of optimized time-memory tradeoff implementation. GPU acceleration is another key feature of RainbowCrack software. By offloading most runtime computation to NVIDIA/AMD GPU, overall hash cracking performance can be improved further.

Several TB of generated rainbow tables for LM, NTLM, MD5 and SHA1 hash algorithms are listed .