Though critics concerned that panel did not adequately address how long telecoms ought to hold NSA’s desired call data

The chief congressional critics of the US National Security Agency said Thursday that a White House review panel report gave them momentum to end bulk domestic surveillance, but expressed reservations about one of the panel’s central proposals.

In an indication of the changing political landscape for the NSA, Representative James Sensenbrenner, the chief House sponsor of a bill preventing the agency from collecting US domestic phone data, said Thursday that “President Obama’s hand-picked panel” highlighted “the need to enact the USA Freedom Act.

But Sensenbrenner, in an interview with the Guardian, was wary of its recommendation that phone companies or other private parties should store communications data for the NSA to search.

"The administration has not yet made the case that increased data retention is necessary, but I welcome any proposals that serve our national security interests without undermining constitutional rights” Sensenbrenner said.

The report by the review group, released Wednesday afternoon, has been greeted warmly by skeptics of mass surveillance, particularly for its recommendations to add privacy advocates at the secret Fisa Court and for endorsing greater use of data encryption.

But as the review group’s recommendations help reshape the debate over bulk surveillance, all sides are girding for a fight over the extent to which any entity ought to hold Americans’ data – a fight likely to determine whether bulk domestic surveillance ends, or continues in a new form.

In line with the USA Freedom Act, the review group rejected a need for the government to hold citizens’ data in bulk, and held out as a solution the ability of the government “to obtain specific information relating to specific individuals or specific terrorist threats” when it can demonstrate to the secret surveillance court “that it has reasonable grounds to access such information.”

But the review group had less to say about a crucial detail: how long the telecoms ought to hold the NSA’s desired call data. It urged the government and the companies to “agree on a voluntary system” and relegated to a footnote a suggestion that two years would be the maximum appropriate period of time to hold the data.

Civil liberties groups who back the USA Freedom Act’s flat prohibition on bulk domestic phone data collection flatly rejected having the phone companies or other “private parties” hold the data for NSA to query.

Alexander Abdo of the ACLU said it would “simply repackage the bulk collection under private control.” Kurt Opsahl of the Electronic Frontier Foundation said it was “still heinous, even if private company servers are holding the data instead of government data centers.” Kevin Bankston of the Open Technology Institute said it would amount to “bulk collection by proxy.”

For its part, the NSA has been publicly hinting for months that as long as the surveillance agency maintains access to a comprehensive database of domestic phone call information going back three to five years, it can live with that database existing outside of the NSA’s Fort Meade campus.

"I would love to give this hornet’s nest to someone else, to say ‘You get stung by this,’” General Keith Alexander, the outgoing director of the NSA, said in October. “But don’t drop it, because that’s our country, and if you do drop it, the chance that a terrorist attack gets through increases.”

On Capitol Hill, where fallout from the review group is unsettled as aides slogged through a lengthy report, pro-reform officials noted that the review group did not endorse the NSA’s call for years.

Now that both a federal judge, Richard Leon, and the review group have both doubted the necessity of bulk collection for stopping terrorist attacks, they argued that the NSA will have difficulty arguing that the companies ought to be required to store the data for as long as the agency wants, especially since the phone companies have not shown enthusiasm for the proposal.

Reform advocates, who have embraced the review group as a political success, were cautious about embracing the telecom-based proposal as a solution for bulk surveillance.

Senator Patrick Leahy, Sensenbrenner’s chief partner in the upper legislative chamber, said that he would hold a hearing in January with the review group to further assess its recommendations.

Senator Ron Wyden, a member of the intelligence committee who said the report in general provided “substantial, meaningful reforms,” indicated on Wednesday that he had concerns about having the companies hold the phone data for the NSA.

“Obviously, there’s going to be a lot of technical issues associated with telecoms having the information,” Wyden told the Guardian in an interview. “That’s going to take some time to work through.”

What the telecoms, NSA and privacy advocates agree on is that requiring the phone companies to hold the data is a complicated process, technologically and otherwise.

Currently, the phone companies typically store customer data for 18 months. The NSA wants the information kept for at least three years and ideally five, ostensibly to detect domestic communications pattern to known terrorist groups. Legislation would be necessary to compel the companies to store the data longer – which is both expensive and raises concerns about keeping the data secure.

The telecoms “would fight tooth and nail” against such a requirement, said a congressional aide, “unless there’s compensations.”

Companies as well keep their data in different file formats, complicating the ability for comprehensive and rapid searches. So far, the telecos have not embraced the proposal.

“A practical concern is that when you start saying you have to keep all this data, you open it up for access to divorce cases and down the line, everyone’s going to want a bite at the apple,” said Ross Schulman, a lobbyist with the Computer and Communications Industry Association.

At the same time, a powerful opponent of the USA Freedom Act, the chairman of the House intelligence committee, worried on Thursday that the review group might weaken US intelligence efforts.

“Though I am still studying the details, I have serious concerns with some of the report’s 46 recommendations,” said Rep. Mike Rogers, a Michigan Republican, former FBI agent and staunch advocate of the NSA’s bulk collection.

"Any intelligence collection reforms must be careful to preserve important national security capabilities. I look forward to working with my colleagues in the Congress to enact meaningful reforms in the near future.”

Senator Dianne Feinstein, Rogers’ counterpart in the Senate, has yet to respond to the review group’s proposals. Feinstein, a California Democrat, is backing an alternative to the USA Freedom Act that would bolster the NSA’s powers to store communications data. Its prospects are less clear in the Senate now that the White House’s surveillance review panel rejected its major rationale.

The USA Freedom Act claims 132 co-sponsors in the House and Senate combined, a quarter of the Congress. Obama has yet to commit to either supporting or opposing it.

“The report sent over by the White House reaffirms what many of my colleagues and I have been saying since June – the NSA has gone too far,” Sensenbrenner said.

“All three branches of government have now said it is time to stop indiscriminately vacuuming up the data of innocent Americans. The report also agrees that the NSA’s bulk collection has come at a high cost to privacy without improving national security.”