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| cryptographic attacks | |
| search algorithms | |
| data structures | |
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Success probability is defined as the probability that the plaintext can be found for a given ciphertext. In the case of passwords, the password is the plaintext, and the hash of the password is the ciphertext, so the success probability is the probability that the original password can be recovered from the password hash. Tables are specific to the hash function they were created for e.g., MD5 tables can only crack MD5 hashes. The theory of this technique was first pioneered by Philippe Oechslin {Link without Title} as a fast form of 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 ineffective against one-way hashes that include Salts . For example, consider a password hash that is generated using the following function (where "+" is the Concatenation operator): hash = MD5(password + salt) To recover the password, a Password cracker would have to generate every possible salt for every possible password — a rainbow table would not necessarily give any benefit. Salts will, in effect, extend the length and potentially the complexity of the password. If the rainbow tables do not have passwords the length (e.g. 8 bytes password, and 2 bytes salt, is effectively a 10 byte password.) and complexity (if the salts aren't alphanumeric, but the database only has alphanumeric passwords) then it will not be found. If found, one will have to remove the salt from the password before it could be used. Nearly all distributions and variations of Unix , Linux , and BSD use hashes with salts, though many PHP web applications use just a hash (typically MD5 ) with no salt. 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
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