In computer science, brute-force search or exhaustive search, also known as generate and test, is a very general problem-solving technique and algorithmic paradigm that consists of systematically enumerating all possible candidates for the solution and checking whether each candidate satisfies the problem's statement.

<programming> A primitive programming style in which the programmer relies on the computer's processing power instead of using his own intelligence to simplify the problem, often ignoring problems of scale and applying naive methods suited to small problems directly to large ones. The term can also be used in reference to programming style: brute-force programs are written in a heavy-handed, tedious way, full of repetition and devoid of any elegance or useful abstraction (see also brute force and ignorance). The canonical example of a brute-force algorithm is associated with the "travelling salesman problem" (TSP), a classical NP-hard problem: Suppose a person is in, say, Boston, and wishes to drive to N other cities. In what order should the cities be visited in order to minimise the distance travelled? The brute-force method is to simply generate all possible routes and compare the distances; while guaranteed to work and simple to implement, this algorithm is clearly very stupid in that it considers even obviously absurd routes (like going from Boston to Houston via San Francisco and New York, in that order). For very small N it works well, but it rapidly becomes absurdly inefficient when N increases (for N = 15, there are already 1,307,674,368,000 possible routes to consider, and for N = 1000 - well, see bignum). Sometimes, unfortunately, there is no better general solution than brute force. See also NP-complete. A more simple-minded example of brute-force programming is finding the smallest number in a large list by first using an existing program to sort the list in ascending order, and then picking the first number off the front. Whether brute-force programming should actually be considered stupid or not depends on the context; if the problem is not terribly big, the extra CPU time spent on a brute-force solution may cost less than the programmer time it would take to develop a more "intelligent" algorithm. Additionally, a more intelligent algorithm may imply more long-term complexity cost and bug-chasing than are justified by the speed improvement. When applied to cryptography, it is usually known as {brute force attack}. Ken Thompson, co-inventor of Unix, is reported to have uttered the epigram "When in doubt, use brute force". He probably intended this as a ha ha only serious, but the original Unix kernel's preference for simple, robust and portable algorithms over brittle "smart" ones does seem to have been a significant factor in the success of that operating system. Like so many other tradeoffs in software design, the choice between brute force and complex, finely-tuned cleverness is often a difficult one that requires both engineering savvy and delicate aesthetic judgment. [Jargon File] (1995-02-14)

<cryptography> A method of breaking a cipher (that is, to decrypt a specific encrypted text) by trying every possible key. The quicker the brute force attack, the weaker the cipher. Feasibility of brute force attack depends on the key length of the cipher, and on the amount of computational power available to the attacker. Brute force attack is impossible against the ciphers with variable-size key, such as a one-time pad cipher. {Breaking ciphers with many workstations (http://distributed.net/projects.html.en)}. (2000-01-16)