The hacker.org challenges are a series of puzzles, tricks, tests, and brainteasers designed to probe the depths your hacking skills. To master this series you will need to crack cryptography, write clever code, and dissect the impenetrable; and in the process you will enrich your understanding of the world of hacking.
The challenges spread out over a mystical map, where solving one challenge opens up paths to ones more difficult. You start in the Neophyte city, and as you prove yourself, progress to ever more tricky and conniving tests.
Hacker points are awareded as follows: players are ranked from top to bottom in order of the sum of the squares of the difficulty of challenges solved. (This encourages solving of more difficult challenges.) The top solver gets 200 points, the next (200 * 0.9), the next (200 * 0.9 * 0.9) and so on.
Some programming challenges use a "King of the Hill" system. In these, you are required not only to pass the tests, but to make the code either fast or small. When another solver beats the current record, they automatically set a new mark to beat. (There may be some window within which one may also get credit for the solution.)
For some challenges, it may be convenient to submit your answer programatically. Much like with the puzzles, you can pass in your username and password as GET or POST parameters. For example, if your username is foo and password is bar, append to the chal.php URL:
http://www.hacker.org/challenge/chal.php?answer=myanswer&id=10&go=Submit&name=foo&password=bar
Please do not abuse this interface to try to guess answers. Aside from putting extra load on the server, we will automatically reject requests that come too frequently.
There is an additional way to submit your answers that doesn't require your password in plaintext. Go to this page and get your submit pw. This can be passed to chal.php as a parameter called 'spw', instead of 'password'.