In the past, 'encryption' was a term closely related to espionage, which entailed the cloak-and-dagger despatch of secretly coded messages by spies from behind enemy lines. But in the modern world of computing, encryption has moved from the realm of the clandestine to that of the commonplace. The use of sophisticated codes and keys to protect private electronic messages has demonstrated the same kind of effectiveness as in sending the communication through a secret courier.

One recent development has been the introduction of new, powerful software that enables anyone with a home computer to encode messages effectively and thus prevent its access to cyber-intruders. A favourite is Boulder (Colorado, US) programmer Phil Zimmerman's PGP or Pretty Good Privacy, which can be downloaded directly from the Net.

Compatible with a large variety of E-mail software used commercially, PGP assigns and manages unique keys for each user. PGP's double key system allows E-mails to be signed by the sender. The person sending an E-mail will just have to encrypt his name at the end using his public key; the receiver can decrypt using his private key. Those advocating privacy on the Internet say that the need for encryption tools has become greater than ever. "E-mail messages are too easy to intercept and scan for keywords," says 7,immerman. Others, however, argue that the number of crimes in which encryption could be used as a tool is infinitesimal.