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Understanding Rainbow Tables

Rainbow tables are precomputed tables that contain hashed passwords and their corresponding plaintext passwords. They allow attackers to crack password hashes by looking up hashes in the tables to find the original password. Rainbow tables exploit weaknesses in password hashing by precomputing hashes for common passwords to conduct dictionary attacks. To prevent the use of rainbow tables, techniques like salting are used, which adds random strings to passwords before hashing to make each hash unique.

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Francis Finan
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184 views1 page

Understanding Rainbow Tables

Rainbow tables are precomputed tables that contain hashed passwords and their corresponding plaintext passwords. They allow attackers to crack password hashes by looking up hashes in the tables to find the original password. Rainbow tables exploit weaknesses in password hashing by precomputing hashes for common passwords to conduct dictionary attacks. To prevent the use of rainbow tables, techniques like salting are used, which adds random strings to passwords before hashing to make each hash unique.

Uploaded by

Francis Finan
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Rainbow tables are precomputed tables that are used to crack password hashes.

Password hashing is a
process of taking a password and converting it into a fixed-size string of characters, called a hash. The
hash is stored in a database instead of the actual password, and when a user attempts to log in, the
password they provide is hashed and compared to the stored hash to determine if the password is
correct. The use of rainbow tables exploits the weakness in this process by using precomputed tables
to quickly guess the original password.

To understand how rainbow tables work, it's important to know that there are two types of hashing
algorithms: one-way and reversible. One-way hashing algorithms are designed to be irreversible,
meaning that it is not possible to reverse the process and obtain the original password from the hash.
Reversible hashing algorithms, on the other hand, are designed to be reversible, meaning that it is
possible to obtain the original password from the hash.

Rainbow tables are designed to attack one-way hashing algorithms by exploiting the fact that many
passwords are relatively simple and can be guessed using a list of common passwords, known as a
dictionary attack. A rainbow table is essentially a precomputed dictionary attack that has been
optimized to take advantage of the specific one-way hashing algorithm being used. The rainbow table
contains a large number of precomputed hashes for every possible password that could be generated
within a certain character set and password length.

When an attacker wants to crack a password, they first obtain the hashed password from the database.
They then compare the hashed password to the precomputed hashes in the rainbow table. If the hash
matches one in the table, the corresponding password is the original password. If the hash is not found
in the table, the attacker can generate a new table that includes the target hash and continue the search.

For example, let's say a user's password is "password123". When the user creates an account, the
password is hashed using a one-way hashing algorithm and stored in the database as a hash, say
"6e15c6cf9545e5a5a437f5ef5a4a4f4c". An attacker who obtains this hash can use a rainbow table to
quickly find the original password by searching for the hash in the table. If the hash is found, the
attacker knows the password is "password123" and can use it to access the user's account.

To prevent the use of rainbow tables, a technique called salting is used. Salting involves adding a
random string of characters to the password before it is hashed, so even if two users have the same
password, their hashes will be different due to the addition of the salt. This makes it much more
difficult to use precomputed tables to crack passwords.

In conclusion, rainbow tables are precomputed tables that are used to crack one-way hashed
passwords. They exploit the fact that many passwords are relatively simple and can be guessed using
a dictionary attack. To prevent the use of rainbow tables, it is recommended to use strong, unique
passwords and to implement salting techniques.

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