Challenge-response
Challenge-response authentication is the common name for the process in which one party presents a question (challenge) and another party must provide a valid answer (response) to be authenticated.
The challenge can be a random number presented to the user, who enters it using his eCode device. The response is then calculated, by way of the user unique-key present on the smart card, token or mobile phone, and presented to the user. The user enters the response back to the service provider site, which authenticates if it is correct or not. The challenge can also be a part of a transaction, for instance the amount of the transaction. Challenge-response combined with a password and/or a PIN is one way to have a Two-Factor Authentication1.
