> [DMCA] section 1201 creates a potential legal obstacle for a researcher or coder if a software vendor employs mechanisms that control the way copyrighted software or other materials can be accessed or used. Many people think of section 1201 as prohibiting cracking digital rights management schemes (DRM). However, the language of section 1201 prohibits more than breaking traditional “copy-protection” mechanisms applied to DVDs and digital video downloads. It also prohibits breaking “access controls”. Software vendors have argued, or are likely to argue, that techniques such as authentication handshakes, code signing, code obfuscation, and protocol encryption all qualify as “technical protection measures” protected by the DMCA.

EFF has an interesting take: https://www.eff.org/issues/coders/reverse-engineering-faq