Thumbprints, retinal scans, electronic signatures and other unique-to-user identification should add another barrier.

CNN: ASIANOW - Asiaweek

The waxy eyes looked as if they would retain thumbprints.

FORBES: Fact and Comment

This is particularly controversial in Spain, because many of the holders of this type of debt are unsophisticated retail customers: horror stories are emerging of illiterate customers signing up for risk-bearing debt with their thumbprints.

ECONOMIST: Bank bondholders