Feds tell Web firms to turn over user account passwords
Secret
demands mark escalation in Internet surveillance by the federal
government through gaining access to user passwords, which are typically
stored in encrypted form.
The U.S. government has demanded that major Internet companies divulge
users' stored passwords, according to two industry sources familiar with
these orders, which represent an escalation in surveillance techniques
that has not previously been disclosed.
If the government is able to determine a person's password, which is
typically stored in encrypted form, the credential could be used to log
in to an account to peruse confidential correspondence or even
impersonate the user. Obtaining it also would aid in deciphering
encrypted devices in situations where passwords are reused.
"I've certainly seen them ask for passwords," said one Internet industry
source who spoke on condition of anonymity. "We push back."
A second person who has worked at a large Silicon Valley company
confirmed that it received legal requests from the federal government
for stored passwords. Companies "really heavily scrutinize" these
requests, the person said. "There's a lot of 'over my dead body.'"
Some of the government orders demand not only a user's password but also
the encryption algorithm and the so-called salt, according to a person
familiar with the requests. A salt is a random string of letters or
numbers used to make it more difficult to reverse the encryption process
and determine the original password. Other orders demand the secret
question codes often associated with user accounts.
"This is one of those unanswered legal questions: Is there any circumstance under which they could get password information?"
--Jennifer Granick, Stanford University
A Microsoft spokesperson would not say whether the company has received
such requests from the government. But when asked whether Microsoft
would divulge passwords, salts, or algorithms, the spokesperson replied:
"No, we don't, and we can't see a circumstance in which we would
provide it."
Google also declined to disclose whether it had received requests for
those types of data. But a spokesperson said the company has "never"
turned over a user's encrypted password, and that it has a legal team
that frequently pushes back against requests that are fishing
expeditions or are otherwise problematic. "We take the privacy and
security of our users very seriously," the spokesperson said.
A Yahoo spokeswoman would not say whether the company had received such
requests. The spokeswoman said: "If we receive a request from law
enforcement for a user's password, we deny such requests on the grounds
that they would allow overly broad access to our users' private
information. If we are required to provide information, we do so only in
the strictest interpretation of what is required by law."
Apple, Facebook, AOL, Verizon, AT&T, Time Warner Cable, and Comcast
did not respond to queries about whether they have received requests for
users' passwords and how they would respond to them.
Richard Lovejoy, a director of the Opera Software subsidiary that operates FastMail,
said he doesn't recall receiving any such requests but that the company
still has a relatively small number of users compared with its larger
rivals. Because of that, he said, "we don't get a high volume" of U.S.
government demands.
The FBI declined to comment.
Some details remain unclear, including when the requests began and
whether the government demands are always targeted at individuals or
seek entire password database dumps. The Patriot Act has been used to demand entire database dumps
of phone call logs, and critics have suggested its use is broader. "The
authority of the government is essentially limitless" under that law,
Sen. Ron Wyden, an Oregon Democrat who serves on the Senate Intelligence
committee, said at a Washington event this week.
Large Internet companies have resisted the government's requests by
arguing that "you don't have the right to operate the account as a
person," according to a person familiar with the issue. "I don't know
what happens when the government goes to smaller providers and demands
user passwords," the person said.
An attorney who represents Internet companies said he has not fielded
government password requests, but "we've certainly had reset requests --
if you have the device in your possession, than a password reset is the
easier way."
Source code to a C implementation of bcrypt, a popular algorithm used for password hashing.
(Credit:
Photo by Declan McCullagh)
Cracking the codes Even if the National Security Agency or
the FBI successfully obtains an encrypted password, salt, and details
about the algorithm used, unearthing a user's original password is
hardly guaranteed. The odds of success depend in large part on two
factors: the type of algorithm and the complexity of the password.
Algorithms, known as hash functions, that are viewed as suitable for
scrambling stored passwords are designed to be difficult to reverse. One
popular hash function called MD5, for instance, transforms the phrase
"National Security Agency" into this string of seemingly random
characters: 84bd1c27b26f7be85b2742817bb8d43b. Computer scientists
believe that, if a hash function is well-designed, the original phrase
cannot be derived from the output.
But modern computers, especially ones equipped with high-performance
video cards, can test passwords scrambled with MD5 and other well-known
hash algorithms at the rate of billions a second. One system using 25 Radeon-powered GPUs that was demonstrated
at a conference last December tested 348 billion hashes per second,
meaning it would crack a 14-character Windows XP password in six
minutes.
The best practice among Silicon Valley companies is to adopt far slower
hash algorithms -- designed to take a large fraction of a second to
scramble a password -- that have been intentionally crafted to make it
more difficult and expensive for the NSA and other attackers to test
every possible combination.
One popular algorithm, used by Twitter and LinkedIn, is called bcrypt. A 2009 paper (PDF) by computer scientist Colin Percival
estimated that it would cost a mere $4 to crack, in an average of one
year, an 8-character bcrypt password composed only of letters. To do it
in an average of one day, the hardware cost would jump to approximately
$1,500.
But if a password of the same length included numbers, asterisks,
punctuation marks, and other special characters, the cost-per-year leaps
to $130,000. Increasing the length to any 10 characters, Percival
estimated in 2009, brings the estimated cracking cost to a staggering
$1.2 billion.
As computers have become more powerful, the cost of cracking bcrypt
passwords has decreased. "I'd say as a rough ballpark, the current cost
would be around 1/20th of the numbers I have in my paper," said
Percival, who founded a company called Tarsnap Backup,
which offers "online backups for the truly paranoid." Percival added
that a government agency would likely use ASICs -- application-specific
integrated circuits -- for password cracking because it's "the most
cost-efficient -- at large scale -- approach."
While developing Tarsnap, Percival devised an algorithm called scrypt,
which he estimates can make the "cost of a hardware brute-force attack"
against a hashed password as much as 4,000 times greater than bcrypt.
Bcrypt was introduced (PDF) at a 1999 Usenix conference by Niels Provos, currently a distinguished engineer in Google's infrastructure group, and David Mazières, an associate professor of computer science at Stanford University.
With the computers available today, "bcrypt won't pipeline very well in
hardware," Mazières said, so it would "still be very expensive to do
widespread cracking."
Even if "the NSA is asking for access to hashed bcrypt passwords,"
Mazières said, "that doesn't necessarily mean they are cracking them."
Easier approaches, he said, include an order to extract them from the
server or network when the user logs in -- which has been done before -- or installing a keylogger at the client.
Sen. Ron Wyden, who warned this week that "the
authority of the government is essentially limitless" under the Patriot
Act's business records provision.
(Credit:
Getty Images)
Questions of law Whether the National Security Agency or FBI
has the legal authority to demand that an Internet company divulge a
hashed password, salt, and algorithm remains murky.
"This is one of those unanswered legal questions: Is there any
circumstance under which they could get password information?" said Jennifer Granick, director of civil liberties at Stanford University's Center for Internet and Society. "I don't know."
Granick said she's not aware of any precedent for an Internet company
"to provide passwords, encrypted or otherwise, or password algorithms to
the government -- for the government to crack passwords and use them
unsupervised." If the password will be used to log in to the account,
she said, that's "prospective surveillance," which would require a
wiretap order or Foreign Intelligence Surveillance Act order.
If the government can subsequently determine the password, "there's a
concern that the provider is enabling unauthorized access to the user's
account if they do that," Granick said. That could, she said, raise
legal issues under the Stored Communications Act and the Computer Fraud
and Abuse Act.
The Justice Department has argued in court proceedings before that it
has broad legal authority to obtain passwords. In 2011, for instance,
federal prosecutors sent a grand jury subpoena demanding the password
that would unlock files encrypted with the TrueCrypt utility.
The Florida man who received the subpoena claimed the Fifth Amendment,
which protects his right to avoid self-incrimination, allowed him to
refuse the prosecutors' demand. In February 2012, the U.S. Court of
Appeals for the Eleventh Circuit agreed, saying that because prosecutors
could bring a criminal prosecution against him based on the contents of
the decrypted files, the man "could not be compelled to decrypt the
drives."
In January 2012, a federal district judge in Colorado reached the
opposite conclusion, ruling that a criminal defendant could be compelled
under the All Writs Act to type in the password that would unlock a
Toshiba Satellite laptop.
Both of those cases, however, deal with criminal proceedings when the
password holder is the target of an investigation -- and don't address
when a hashed password is stored on the servers of a company that's an
innocent third party.
"If you can figure out someone's password, you have the ability to reuse
the account," which raises significant privacy concerns, said Seth Schoen, a senior staff technologist at the Electronic Frontier Foundation.
Last updated at 8:00 p.m. PT with comment from Yahoo, which responded after this article was published.
Disclosure: McCullagh is married to a Google employee not involved with this issue.
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