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How do rainbow tables work?
Rainbow tables are tables of reversed hashes used to crack password hashes. When a computer user enters a password, the system hashes the password and compares it to the stored hash. If the hashes match, the user is given access. Rainbow tables use precomputed hashes in an attempt to recover the prehashed password.
How does a rainbow table help an attacker?
A rainbow table is a database that is used to gain authentication by cracking the password hash. It is a precomputed dictionary of plaintext passwords and their corresponding hash values that can be used to find out what plaintext password produces a particular hash.
What is the purpose of rainbow table?
A rainbow table is a precomputed table for caching the output of cryptographic hash functions, usually for cracking password hashes. Tables are usually used in recovering a key derivation function (or credit card numbers, etc.) up to a certain length consisting of a limited set of characters.
How does the reduction function work in rainbow table?
So that the required storage space doesn’t get out of hand, rainbow tables use a reduction function that change the hash value into plaintext. Important: The reduction function doesn’t reverse the hash value, so it doesn’t output the original plaintext (i.e. the password) – because this isn’t possible – but instead outputs a completely new one.
Is there a way to recalculate a rainbow table?
There’s no way to recalculate the operation. Hackers use brute force attacks instead: with this, a computer program keeps guessing until it’s found the correct character sequence. This method can also be combined with password dictionaries.
How are rainbow tables used to recover passwords?
The hashing function for a given set of Rainbow Tables must match the hashed password you want to recover. The reduction function must transform a hash into something usable as a password. A simple reduction function is to Base64 encode the hash, then truncate it to a certain number of characters.
What are the steps of a rainbow table attack?
A rainbow table attack eliminates this need by already computing hashes of the large set of available strings. There are two main steps in this: Here, the hash of a string is taken and then reduced to create a new string, which is reduced again, repeatedly.