recently, I got interested in an assignment, which was to deassemble a program and crack the password in it. and i remember that I enjoyed trying sql injection to a security problem given by a friend.
I wonder if there's a site with cracking problem sets or competing with others. but I wasn't able to find one for hours of searching.
thank you
Code bashing teaches the skills, but can't really compete with others, and is a commercial site: https://www.codebashing.com
Secure code warrior is also a commercial site. It teaches the skills and allows you to compete with others from your organisation: https://new-www.securecodewarrior.com
OSCP is commercial, teaches you how to do network pentesting, and has a number of challenge systems for you to hack into. Really fun and insightful, and if you commit yourself, you may end up with one of the best certifications in the industry. But it is a huge time commitment.
There are lots of free places to practice and learn, such as web goat (downloadable tool), Altoro mutual (pretend bank site, easy to hack into), crypto pals (learn to crack cryptography), bodgeit store (similar to web goat), etc....