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In cryptanalysis and computer security, password cracking is the process of guessing passwords [1] protecting a computer system.A common approach (brute-force attack) is to repeatedly try guesses for the password and to check them against an available cryptographic hash of the password. [2]
When password-guessing, this method is very fast when used to check all short passwords, but for longer passwords other methods such as the dictionary attack are used because a brute-force search takes too long. Longer passwords, passphrases and keys have more possible values, making them exponentially more difficult to crack than shorter ones ...
Attempting to crack passwords by trying as many possibilities as time and money permit is a brute force attack. A related method, rather more efficient in most cases, is a dictionary attack. In a dictionary attack, all words in one or more dictionaries are tested. Lists of common passwords are also typically tested.
A rainbow table is a precomputed table for caching the outputs of a cryptographic hash function, usually for cracking password hashes.Passwords are typically stored not in plain text form, but as hash values.
The salt and hash are then stored in the database. To later test if a password a user enters is correct, the same process can be performed on it (appending that user's salt to the password and calculating the resultant hash): if the result does not match the stored hash, it could not have been the correct password that was entered.
To this end, penetration testers and attackers can harvest password hashes using a number of different methods: Cached hashes or credentials of users who have previously logged onto a machine (for example at the console or via RDP) can be read from the SAM by anyone who has Administrator-level privileges.
One of the modes John can use is the dictionary attack. [6] It takes text string samples (usually from a file, called a wordlist, containing words found in a dictionary or real passwords cracked before), encrypting it in the same format as the password being examined (including both the encryption algorithm and key), and comparing the output to the encrypted string.
Passwords or passphrases created by humans are often short or predictable enough to allow password cracking, and key stretching is intended to make such attacks more difficult by complicating a basic step of trying a single password candidate. Key stretching also improves security in some real-world applications where the key length has been ...