If the bank finds that the user answers in short order all its many questions correctly, it will transfer to his laptop a cookie which includes an encrypted token, which further includes a key and a "hash number".

ECONOMIST: Fake ID cards

The hash number is a device which permits the software evaluating the key to know whether the key has been tampered with since it was last written.

ECONOMIST: Fake ID cards

If any one of these things is out of place, or if the hash number no longer properly reflects the state of the encrypted key as recorded on the laptop, then, the user will have to go through the entire process of registering himself on the site, again.

ECONOMIST: Fake ID cards