There are multiple ways to crack passwords, and using a rainbow table is one of them. But don’t be fooled by the innocent-sounding name — this is still a form of cybercrime worth looking into. Read on to find out what a rainbow table attack is and how to protect yourself from it.
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A rainbow table attack is a form of cyberattack for cracking password hashes that uses a special table consisting of precomputed strings or commonly used passwords and corresponding hashes. A rainbow table attack works on passwords that are hashed — protected by using the hashing method — so let’s look into hashing first.
Hashing is the process of transforming any given key or string of characters (such as a password or username) into another string of characters (a different value, also known as the hash value) to make it unreadable and unusable for cybercriminals. This is done by running the password through a one-way mathematical algorithm called a hash function. Hashed passwords are then stored on the company’s server.
If a company uses hashing, it doesn’t have to store the actual passwords to verify legitimate users. Whenever a user enters a password, it is converted into a hash value, which is then compared to the hash value stored on the company’s servers. If the values match, the user is authenticated and granted access. Unfortunately, hashing algorithms are also vulnerable to attacks such as the rainbow table attack. But how do they work?
Rainbow tables are constructed using chains of hashing and reduction operations. A hash function links plaintexts to their hash values, while the reduction function links hash values to plaintexts.
This whole process has four steps, listed below:
Rainbow tables contain very large sets of strings, which means they require large amounts of storage space, sometimes taking up terabytes. They can also take a long time to generate. However, rainbow table attacks are more efficient than brute-force or dictionary attacks because hashes are checked against a stored hash database, so you don’t need to repeat the hashing process from the beginning each time.
Both rainbow table attacks and dictionary attacks are password-cracking techniques used by hackers to gain access to passwords.
In a dictionary attack, the hacker uses a pre-compiled list of common passwords (popular words and symbols), the “dictionary,” to compare against the hashed passwords. If they find a match, it means the hashed password has been cracked. Dictionary attacks are effective because many people use simple passwords that are easy to guess. These attacks rely on the speed of a computer to try a large number of possible passwords.
In a rainbow table attack, the attacker uses a precomputed table of hashes to look up the plaintext version of a hashed password. Unlike a dictionary attack, where the attacker tries every word in the dictionary until they find a match, a rainbow table attack allows the attacker to quickly find the plaintext password if it exists in the precomputed table. Rainbow tables attacks require less computing power and are much faster than standard dictionary attacks, but they require more time to create and use up more space.
There are several ways how a hacker can gain unauthorized access to hashes and carry out rainbow table attacks:
Salting is one of the ways to protect your data, but it’s not the only one.
You can prevent rainbow table attacks and protect your data in several ways:
A widespread use of salting techniques and other more effective password cracking methods have made rainbow table attacks nearly obsolete. Nevertheless, staying alert and taking the abovementioned precautions will help you stay safe against these and other attacks.
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