Federal prosecutors want a judge to order a Colorado woman to provide the password to decrypt her laptop, which the government seized with a search warrant.

With backup from digital rights groups, the woman is fighting the feds, arguing that being forced to provide her password violates the Fifth Amendment’s protection against forced self-incrimination.

Colorado U.S. District Judge Robert Blackburn is expected to rule any day on whether to force defendant Ramona Fricosu to decrypt her Toshiba Satellite M305, which authorities seized from her in 2010 with a court warrant while investigating financial fraud.

The case is being closely watched by digital rights groups, as the issue has never been squarely weighed in on by federal courts, and the Supreme Court has never addressed the issue.

But a factually similar dispute involving child pornography ended with a Vermont federal judge ordering the defendant to decrypt the hard drive of his laptop. While that case never reached the Supreme Court, it differed from the Fricosu matter because U.S. border agents already knew there was child porn on the computer because they saw it while the computer was running during a 2006 routine stop along the Canadian border.

The Electronic Frontier Foundation’s Marcia Hoffman said (.pdf) in a court filing that the very act of requiring Fricosu to input her password into the laptop would be incriminating “because it might reveal she had control over the laptop and the data there.”

Assistant U.S. Attorney Patricia Davies said(.pdf) said there is no Fifth Amendment breach, and that it might “require significant resources and may harm the subject computer” if it tried to crack the encryption.

Full disk encryption is an option built into the latest flavors of Windows, Mac OS and Linux, and well-designed encryption protocols used with a long passphrase can take decades to break, even with massive computing power.

The authorities countered the EFF, telling Judge Blackburn that the “government knows that the defendant had access to, and control over, the subject computer immediately prior to the search warrant execution because it was found in her bedroom, on top of the laptop case.”

The feds also played the terror card.

Davies said that, if the defendant is not compelled to unlock her computer, that would amount “to a concession to her and potential criminals (be it in child exploitation, national security, terrorism, financial crimes or drug trafficking cases) that encrypting all inculpatory digital evidence will serve to defeat the efforts of law enforcement officers to obtain such evidence through judicially authorized search warrants, and thus make their prosecution impossible.”

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