This is an old revision of this page, as edited by 131.215.155.151 (talk) at 10:52, 4 January 2006 (→External links). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.
Revision as of 10:52, 4 January 2006 by 131.215.155.151 (talk) (→External links)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)A rainbow table is a special type of lookup table that is constructed by placing a plaintext password entry in a chain of keys and cyphertexts, generated by a one-way hash. The end result is a highly compressed table that contains statistically high chance of revealing a password within a short period of time, generally less than a minute. The success probability of the table depends on the parameters used to generate it. These include the character set used, password length, chain length, table count. Tables are hash specific, e.g. MD5 tables can only crack MD5 hashes. The theory of this technique was first pioneered by Philippe Oechslin as a fast form of time-memory tradeoff (PDF), which he implemented in the Windows password cracker Ophcrack. The more powerful RainbowCrack program was later developed that can generate and use rainbow tables for a variety of character sets and hashing algorithms, including LM hash, MD5, SHA1, etc.
Defense against rainbow tables
A rainbow table is essentially worthless against one-way hashes that include tokens (or salts, in the case of 56-bit DES). For example, if a password hash is generated using the following function (where "." is the concatenation operator):
hash = md5sum(password . token)
...a password cracker would have to generate both every possible token for every possible password — a rainbow table would not give any benefit. However, if a password hash is generated using the following function:
hash = md5sum(password)
...a password cracker may benefit from a rainbow table.
Nearly all distributions and variations of Unix, Linux, and BSD use one-way hashes and salts, though many PHP web applications use regular MD5. The Windows NT/2000 family of windows uses the LAN Manager and NT LAN Manager hashing method and is also unsalted, which make it one of the more popularly generated tables.
External links
- Project RainbowCrack - Official site.
- RainbowCrack Tutorial - Tutorial on using Rainbow Tables.
- winrtgen - GUI for rtgen.
- Plain-Text Team - Largest Distributed Rainbow Table Cracking System (over 600gb of tables); free LM/NTLM/MD5 online cracking
- PassCracking.com - free MD5 online cracking (CLOSED)
- PassCracking.ru - free MD5 online cracking + database (down?)
- milw0rm.com - free LM/MD5 online cracking
- rainbowtables.shmoo.com - Free LanMan rainbow tables.
- rainbowcrack.com - Community based distributed rainbow table generation
 | This computing article is a stub. You can help Misplaced Pages by expanding it. |