Read the excerpt from the code book.

however, as with every technology, there is a dark side to encryption. as well as protecting the communications of law-abiding citizens, encryption also protects the communications of criminals and terrorists. currently, the police use wiretapping as a way of gathering evidence in serious cases, such as organized crime and terrorism, but this would be impossible if criminals used unbreakable ciphers. as we enter the twenty-first century, the fundamental dilemma for cryptography is to find a way of allowing the public and business to use encryption in order to exploit the benefits of the information age without allowing criminals to abuse encryption and evade arrest. there is currently an active and vigorous debate about the best way forward, and much of the discussion has been inspired by the story of phil zimmermann, a man whose attempts to encourage the widespread use of strong encryption have panicked america's security experts, threatened the effectiveness of the billion-dollar national security agency, and made him the subject of an fbi inquiry and a grand jury investigation.

which detail is most relevant to the claim that there is a "dark side to encryption”?

1. zimmermann encourages everyone to use strong encryption.
2. criminals could use encryption to avoid the law and cause terror.
3. zimmermann has made security experts panic because of his encryption.
4. encryption software can protect the privacy of law-abiding citizens.