Question

I’ve been working on a brute force program in C++ that for the time being only deals with alpha numeric values (lower case only), and a password of unknown length.

I’m working with a quad core computer so I’ve broken the list of possibilities into four sections and have one thread working on each.

The sections are:

000...0 to 8zz...z
900...0 to hzz...z
i00...0 to qzz...z
r00...0 to zzz...z

Could I make better use of threading to increase the speed? Since only 1 of 4 threads will ever reach the password it feels like 3/4 of the program is a waste of time.

It would seem that if I could have the threads work together somehow it would be more efficient, however I can’t seem to think of a way to do this.

Any advice is much appreciated, I’m quite new to threading.

*EDIT: I should clarify that because it’s a fairly simple program for academic purposes, I am actually only cracking one password, and giving the signal to kill the remaining 3 threads once one finds it. *

Answer 1

Here are some ideas:

• You can use an atomic boolean variable to communicate across the threads that the password has been found. Each thread just has to check periodically (for example, just before attempting the next password) if the flag has been set.
• Instead of statically dividing the work in four equal parts, you could also use one central list of passwords to try and let each thread grab items as they need it.