Authentication and confidentiality are issues that have fascinated scientists and mathematicians for centuries. Matt Nicholson looks at some of the techniques in use today.

Originally published DNJ Online, May 2006

A man walks into a bank and presents a cheque to the cashier. The cheque is made out in the man’s name, but the cashier refuses to cash the cheque. Why?

There could be many reasons. The cashier could suspect the cheque has been tampered with so as to pay out a larger sum than the payer intended. The cashier could suspect that the customer is not who he claims to be, or that the driving licence he presents as identification is a forgery.

Whatever the scenario, secure communication essentially comes down to authentication and confidentiality. In the real world, authentication is achieved through a passport or a signature, and confidentiality through a sealed envelope or locked safe. In the digital world authentication is achieved through knowledge of a secret code, such as a password or a PIN (Personal Identification Number), and confidentiality through encryption. Read More