Password Cracking Techniques in this article explain different types of password cracking techniques and tools.
There are three popular techniques for password cracking:
Method 1: Dictionary Attacks
In a dictionary attack, a dictionary file is loaded into the cracking application that runs against user accounts. A dictionary is a text file that contains a number of dictionary words or predetermined character combinations. The program uses every word present in the dictionary to find the password. Dictionary attacks are more useful than a brute-force attack. However, this attack does not work against a system that uses the passphrases or passwords not contained within the dictionary used.
This attack is applicable in two situations:
- In cryptanalysis, it helps to find out the decryption key for obtaining the plaintext from the ciphertext.
- In computer security, it helps to avoid authentication and to access a computer by guessing passwords.
Methods to improve the success of a dictionary attack:
- Use more number of dictionaries, such as technical dictionaries and foreign dictionaries that help to retrieve the correct password.
- Use the string manipulation on the dictionary, i.e., if the dictionary contains the word, “system,” then try string manipulation and use “metsys” and others.
Method 2: Brute-Forcing Attacks
Cryptographic algorithms must be hard enough to prevent a brute-force attack. The definition, stated by RSA is, “Exhaustive key-search, or brute-force search, is the basic technique for trying every possible key in turns until the correct key is identified.”
Brute-force attack refers to the process of trying each and every single of the encryption keys to find the required information. Brute-force attacks need more processing power compared to other attacks.
A brute-force attack is basically a cryptanalytic attack used to decrypt any encrypted data. In other words, testing all possible keys is an attempt to recover the plaintext, which is the base for producing a particular ciphertext. The detection of key or plaintext at a faster pace compared to the brute-force attack is the process of breaking the cipher. A cipher is secure if no method exists to break that cipher other than a brute-force attack. Mostly, all ciphers lack mathematical proof of security.
Some considerations for brute-force attack are as follows:
- It is a time-consuming process.
- Can eventually trace all passwords.
- An attack against Networking Technology (NT) hash is much harder against LAN Manager (LM) hash.
Related Product : Computer Hacking Forensic Investigator | CHFI
Method 3: Rule-based Attack
Attackers use the rule-based attack when they know some credible information about the password, such as rules of setting the password, algorithms involved, or the strings and characters used in its creation. For example, if the attackers know that the password contains a two- or three-digit number, then they will use some specific techniques to extract the password in less time.
By obtaining useful information, such as use of numbers, the length of password, and special characters, the attacker can easily adjust the time for retrieving the password to the minimum and enhance the cracking tool to retrieve passwords. This technique involves brute-force, dictionary, and syllable attacks. The attackers may use multiple dictionaries, brute-force techniques, or simply try to guess the password.
Default Passwords
Default passwords refer to those supplied by the manufacturers with new equipment. Usually, default passwords provided by the manufacturers of password-protected devices allow the user to access the device during initial setup and then change the password. But often, an administrator will either– forget to set the new password or ignore the password-change recommendation and continue to use the original password. Attackers can exploit this lapse and find the default password for the target device from manufacturer websites to successfully access the target device.
Using Rainbow Tables to Crack Hashed Passwords
A rainbow table is a lookup table specially used in recovering a plaintext password from a cipher text. It consists of a table with all possible plaintext combinations for encrypted passwords created using a specific hash algorithm. The table contains word lists such as dictionary files and brute-force lists along with their computed hash values.
The attacker uses this table to look for the password and tries to recover it from password hashes. An attacker computes the hash for a list of possible passwords and compares it to the pre-computed hash table (rainbow table), If attackers find a match, they can crack the password.
A rainbow attack is the implementation of the cryptanalytic time-memory trade-off technique. In this attack, the intruders use already calculated information stored in the rainbow tables. They store the password hash table in the memory and use it to extract plaintext password from a ciphertext.
It is easy to recover passwords by comparing captured password hashes to the pre-computed tables.
Also Read : Anti-Forensics Techniques: Password Protection
Tools to Create Rainbow Tables: rtgen and Winrtgen
Attackers can create rainbow tables by using the following tools.
1. rtgen
source: http://project-rainbowcrack.com
RainbowCrack is a general purpose implementation tool that takes advantage of the time-memory trade-off technique to crack hashes. This project allows you to crack a hashed password. The rtgen tool of this project helps to generate the rainbow tables. The rtgen program needs several parameters to generate a rainbow table.
2. Winrtgen
Source: http://www.oxid.it
Winrtgen is a graphical Rainbow Tables Generator that helps attackers to create rainbow tables from which they can crack the hashed password.
Generate Rainbow Tables Using Winrtgen:
- Download and install Winrtgen.
- Click the Add Table button.
- In the Rainbow Table properties window, set up all of the properties, and click OK.
- In the main program, click OK.
Questions related to this topic
- What is the difference between a dictionary password attack and a brute force password attack?
- What is the name of an attack that scans a prearranged list of words to guess your password?
- What limits how fast a password for an encrypted file is cracked?
- What is dictionary attack on password?
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