Just when Americans were finally getting used to using chips on our credit cards, Visa and Mastercard are looking to introduce another security feature: fingerprint sensors embedded in the cards themselves.

The Wall Street Journal reports that the two giants of plastic-based purchases are in the early stages of adding biometric security measures to their cards.

The technology works in the same fashion as fingerprint sensors on smartphones. When you first get a card, you register your fingerprint on it and then each time you make a purchase you place your finger on the sensor and the card will check to make sure the print matches the one it has stored for the card's owner.

There are a number of issues complicating what might seem like a straightforward feature here, however.

First, there's the notion that attaching fingerprints to transactions could actually introduce a new security vulnerability into the system, giving hackers and identity thieves a new data point to target, steal and exploit.

So far this hasn't been much of a problem with fingerprint sensors on phones, at least not yet.

Then there's the big question of cost. Banks would have to shoulder the cost of re-issuing all new cards with the fancy new sensors right after shelling out to send us all new chip cards.

There's little motivation for card issuers to make that investment in security when very few customers are clamoring for fingerprint sensors. Mastercard has run a pilot of the cards in South Africa and Visa ran a U.S. fingerprint debit card pilot through Mountain America Credit Union earlier this year. According to WSJ, only 130 people signed up for the American program.

Of course, there is another solution to making transactions more secure. It's called blockchain, but it's a whole other can of worms that many banks consider a threat and most consumers don't yet understand.

At the same time though, big names in finance like American Express and Santander are experimenting with their own blockchain implementations and flirting with existing cryptocurrencies and tokens such as Ripple.