The measure of man

ON THE Internet, goes the old gag, nobody knows you're a dog. The usual way to prove who you are when picking up e-mail, shopping online or visiting a closed area of a website is to type in a password—a surprisingly old-fashioned form of security that would be recognisable to a Roman soldier. But though passwords are simple, they are far from secure. Many people use the same one for everything. Worse, they may use a common word such as “hello”, their phone number or their dog's name—any of which could be guessed by an intruder.