Credit cards are a favorite target of thieves, accounting for more than 67% of the losses, cites a U.S. Federal Trade Commission study. Some 30% of people write their personal ID number on back of ATM cards, making it even easier for thieves.

Existing biometric authentication systems such as fingerprint scanners could secure credit-card transactions, though credit-card providers have been slow to adopt the technology. Services offered by BioPay LLC, Herndon, Va., and PayByTouch, San Francisco, already let shoppers pay for groceries by pressing their fingers on a sensor mounted near the cash register — no card needed. Millions of cell phones and laptops as well have fingerprint sensors that act as locks and replace text-based log-ins. When and if credit-card companies follow suit remains unclear. The biometrics market is doing well without them, however. It grew 29% last year and could reach $3.4 billion in 2007.