Circumvention usually means "to decrypt an encrypted work, decrypt an encrypted piece, or otherwise avoid, circumvent, remove, deactivate, or damage a technological measure without the copyright holder's permission. Reverse engineering, on the other hand, is the scientific method of disassembling something to understand how it works. While not all circumvention acts require reverse engineering, reverse engineering of works protected by technological mechanisms requires circumvention. Placing digital protection systems on copyrighted works essentially restricts access to the information that the reverse engineer seeks to know about how the product works.