If one part of some lawmakers' plan for comprehensive immigration reform goes through, Social Security cards could soon come with a fingerprint.

Senators John McCain (R-Ariz.) and Chuck Schumer (D-N.Y.) said on Thursday that their Senate framework for immigration reform, recently endorsed by Senate Majority Leader Harry Reid (D-Nev.), could require biometric information to check employment status.

Asked whether he favored "a super Social Security card that would have some sort of biometric thing like a fingerprint" by Politico's Mike Allen at a Politico Playbook breakfast on Wednesday, McCain said, "I'm for it."

McCain said he was not sure "exactly how" such a proposal would play out in any legislation, "but there is technology now that could give us a Social Security card, people a Social Security card, that is tamper-proof."

"We want to make sure that employers do not hire people who are here illegally," said Schumer, who has called for biometric employment cards in the past. "The only way to do that is to have a non-forgeable card. Because right now you can go down the street here and get a Social Security card or a driver's license for $100 that's forged."

The White House did not respond to a request for comment Thursday, but McCain and Schumer's proposal sounds similar to President Barack Obama's call in his immigration reform outline for a "fraud-resistant, tamper-resistant" Social Security card and "new methods to authenticate identity."

Biometrics proposals have been floated for years as one solution to the vexing problem of how to prove workers are who they say they are. The ID card industry sees the potential for billions of dollars of business if immigration reform leads to biometric requirements. Privacy advocates, however, worry the new proposals could in essence create a national ID -- and lead to a spate of Arizona-style "show-me-your-papers" laws.

Some of the estimated 11 million undocumented immigrants currently in the United States resort to using forged or stolen Social Security identities to obtain work. A computer system called E-Verify is supposed to catch people who are not authorized to work in the United States, but it goes no further than matching a name to a number, and its use is usually voluntary.

Moreover, E-Verify "has too many false negatives and false positives," Schumer said. A 2008 government study concluded that 0.8 percent of authorized workers are identified as unauthorized by the system, and 54 percent of unauthorized workers were tagged as authorized. With hundreds of thousands of employers signed up for E-Verify, and millions of workers covered, the mistakes add up -- and even for American-born citizens, proving identity can sometimes turn into a bureaucratic nightmare.

Schumer's solution is to require some sort of biometric information, like a photo, a fingerprint or an iris scan, to go along with Social Security cards. The biometrics would provide a verifiable external check on the bare Social Security number.

Civil liberties advocates, however, caution that linking biometric identifiers to Social Security cards would inevitably create momentum toward a national ID card.

"Once you have a physical card, people are going to start asking for it," said Chris Calabrese, legislative counsel for the American Civil Liberties Union. "If you look like you might be undocumented, are police going to expect to see your card on the street? We've seen these kinds of status checks in places like Arizona in the past."

Representatives of the biometrics industry claim the cards could be made in a way that respects privacy and prevents official misuse.

"What it really comes down to is: how do we deal with an identity environment and make sure we're empowering the citizen? How do we let them be the one that's in control of their identity?" said Kelli Emerick, executive director of the Secure ID Coalition, an industry group. "There are ways in implementation that can be very sensitive to privacy."

Emerick suggested an ID that included a photo on a chip embedded in the card, not stored in a centralized database. "I think that could definitely be a possibility," she said. "And maybe that's something that's voluntary: If you want to harden your credential and add this piece to it, that's a possibility." (Obama's proposal suggests "a voluntary pilot program to evaluate new methods to authenticate identity.")

But Calabrese countered that such a technique would mean that "any time you lost your card you'd have to go back, go through the entire process again to get your card reissued" -- an impractical solution, he said.

Whatever the mechanics of the biometric cards, the political pitfalls both for the Obama administration and Congress are clear. The 9/11 Commission recommended hardened standards for state ID cards, but the resulting REAL ID Act ran into a firestorm of controversy. States objected to the costs of upgraded cards, and a coalition of civil libertarians and conservatives concerned about government overreach managed to slow the law's implementation to such an extent that the Department of Homeland Security says so far only 13 states have met the law's standards.

Schumer also suggested linking employment verification and biometrics the last time immigration reform was on the table, in 2009, to similar objections. ID industry executives estimated they could make anywhere from $1 billion to $4 billion off the idea -- but it went nowhere. Emerick chalked the response up to "the politics around immigration at that time."

But Calabrese doesn't see the civil liberties objections to biometrics, or anything approaching a national ID, fading any time soon.

"Imagine the police holding their smartphones with their E-Verify app, and they walk up to you on the street and say, 'What's your name?'" he said. "It's an enormously intimidating prospect, this idea that they've got a national database."

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