Brute force attack

The Electronic Frontier Foundation's US$250,000 DES cracking machine has over 1,800 custom chips and could brute-force a DES key in a matter of days.

A brute force attack is a term in cryptanalysis. It means trying to break a coded cyphertext by trying a lot of possibilities with fast computers. For example, a large number of the possible keys are tried in the key space. If successful , this decrypts the encrypted message.

Overview

The theoretical possibility of a brute force attack is recognized by the cryptographic system designers. They work to make the cryptographic system very difficult for computers to break using brute force attack. For that reason, one of the definitions of "breaking" a cryptographic scheme is to find a method faster than a brute force attack.

The selection of an appropriate key length depends on how difficult it will be to break it using a brute force attack. By obfuscating the data before encryption, brute force attacks are less effective and more difficult to determine.

The brute force attack can be used together with a dictionary attack.

For symmetric encryption, a key size of 128 bits is considered secure against brute force by traditional computers. 192 or 256 bits is considered secure against quantum computers. Many old ciphers, such as DES, used short keys which made them breakable by brute force.