Criminals have at their disposal a variety of technologies for hiding communications and evidence stored on computers from law enforcement. These include encryption, passwords, digital compression, steganography, remote storage, and audit disabling. They can also hide crimes through anonymity tools and techniques such as anonymous remailers, anonymous digital cash, looping, cloned cellular phones, and cellular phone cards. This paper discusses use of these technologies by criminals and terrorists, and how that use has affected investigations and prosecutions. Options available to law enforcement for dealing with the technologies, especially encryption, are also discussed. Numerous case studies are presented for illustration.

Encryption is essential in today’s information and network age. Encryption policy must facilitate and encourage the use of encryption so that businesses can protect their corporate assets from economic espionage by foreign governments and competitors, so that law enforcement agencies can counter the surveillance activities of organized crime, and so that all organizations and individuals can safeguard sensitive information from criminals and intruders. At the same time, because encryption can be exploited by criminals and terrorists, its completely unfettered proliferation may not be in our national interest. The Clinton administration and National Research Council reached a similar conclusion, although they recommended different approaches.