Crackme

A crackme (often abbreviated by cm) is a small program designed to test a programmer's reverse engineering skills.

They are programmed by other reversers as a legal way to crack software, since no intellectual property is being infringed upon.

Crackmes, reversemes and keygenmes generally have similar protection schemes and algorithms to those found in proprietary software. However, due to the wide use of packers/protectors in commercial software, many crackmes are actually more difficult as the algorithm is harder to find and track than in commercial software.