Fingerprint Authentication And The Fifth Amendment

-Submitted by David Drumm (Nal), Guest Blogger

iphone_fingerprintThe iPhone 5s allows the user to unlock their device using biometric data, namely their fingerprint. It is more convenient that typing in a simple four digit passcode. Fingerprint readers vary in vulnerability. Some only check ridges and can be fooled by a good photocopy. The iPhone reader uses radio frequency scanning to detect sub-epidermal layers of your skin requiring the owner to be alive and the finger attached. The new fingerprint reader may protect your iPhone from thieves, but what about protecting your personal data from government snooping?

The Fifth Amendment provides that no person “shall be compelled in any criminal case to be a witness against himself.” In Miranda v. Arizona, the Supreme Court extended Fifth Amendment protections to encompass situations outside the courtroom that involve curtailment of personal freedom. In Fisher v. United States (1976), the Supreme Court held:

The Fifth Amendment does not independently proscribe the compelled production of every sort of incriminating evidence but applies only when the accused is compelled to make a Testimonial communication that is incriminating.

The Court realized the communicative aspects of producing evidence in response to a subpoena and hence, testimony is more broadly understood as an act that explicitly or implicitly conveys a statement of fact.

In the case of United States v. John Doe (2012), Judge Tjoflat, writing for the United States Court of Appeals for the Eleventh Circuit, noted that the “touchstone of whether an act of production is testimonial is whether the government compels the individual to use “the contents of his own mind” to explicitly or implicitly communicate some statement of fact.”

The classic example, from United States v. Hubbell (2000), is the government forcing someone to turn over a key to a lockbox versus demanding the combination to a wall safe. The combination would be “testimonial” because the person would be revealing contents of their mind. Turning over the key would not be “testimonial.” In Fisher, the 11th Circuit Court explained:

the decryption and production of the hard drives would require the use of the contents of Doe’s mind and could not be fairly characterized as a physical act that would be nontestimonial in nature. We conclude that the decryption and production would be tantamount to testimony by Doe of his knowledge of the existence and location of potentially incriminating files; of his possession, control, and access to the encrypted portions of the drives; and of his capability to decrypt the files.

The compelled production of biometric data, such as a fingerprint, to unlock an iPhone would appear nontestimonial in nature.

In a Wisconsin case, federal prosecutors dropped their demands for decryption key when the FBI revealed it had cracked two of the suspect’s drives, both Western Digital My Book Essentials. Western Digital declined comment. The FBI is working on decrypting the other seven drives. An astute defense attorney might suspect that encryption keys were provided to the FBI by manufactures without a warrant.

While using a voiceprint as authentication would be prima facia “testimonial,” the key phrase would often be used in public and easily recorded.

The new iPhone’s fingerprint authentication feature is convenient and an excellent deterrence to theft. It is unlikely to provide any Fifth Amendment protection of your personal data. It is also a boon for our kitteh overlords:

H/T: Marcia Hofmann, Adario Strange, Kevin Cole, Anthony A. De Corso, Hanni Fakhoury.

28 thoughts on “Fingerprint Authentication And The Fifth Amendment”

  1. When I wrote I was going to pass on Tony’s advice I meant I was going to give it to my son-in-law. Which I did.

    He responded that the finger print algorithm is just one more piece of information to be added to the database which could then be combined with say a picture of oneself from Facebook or twitter or the DMV … well you get the picture.

    The government already makes a ton of money selling databases so, I guess, this could eventually become one more money making scheme for them or for Apple.

    Predictive analytics, dynamic content … there is even an Israeli company that has developed or is developing a dynamic video content personalized video ad for email marketing.

    With all of this new technology and databases some retailers could get themselves into real trouble.

  2. Nal: [Tim Cook claims:] It isn’t possible for your actual fingerprint image to be reverse-engineered from this mathematical representation.

    Maybe not, but I’m going to call BS on Tim Cook. This is probably a fine application for a genetic algorithm; to start with some population of finger prints, evaluate each according to this mathematical algorithm, and slowly modify the fingerprints at random to evolve an ever better match until the result matches well enough to unlock the phone.

    And, if one’s actual fingerprints are already on file (as mine are for a security clearance in the military), then running the Apple algorithm to produce a digital signature for each is a no-brainer, and producing the exact image (of all the fingerprints) is just looking up the fingerprint set by the digital image produced.

    Beyond that, getting one’s “actual fingerprint” may not be necessary anyway. If the “mathematical representation” of my fingerprint can be shown to be unique enough to make the probability of somebody else matching nearly non-existent, then that by itself could be used as pretty convincing circumstantial evidence that I owned the phone, made the calls, and was responsible for its contents and messaging.

    For example, suppose the prosecutor tells the jury that with the help of Apple and the FBI the iPhone algorithm was run on ten million fingerprints, and mine was the only one that produced the “mathematical signature” needed to actually open the iPhone in question. I think that would be, to the jury, equally as convincing as the testimony of a fingerprint expert.

  3. Yesterday I wanted to ask my son-in-law why he was standing in line at the apple store at 3:45 in the morning to buy a new phone. (I didn’t ask for he would look upon that display of interest as an excuse to buy me said device with appropriate data-plan [I have no idea what a data plan is].) Thanks to Nal, I now understand.

    I bought him one of those spiffy wallets that protects his cards and license from scanners (I don’t know if they actually work but it was my birthday present to everybody this year) and he counters that move for privacy with this purchase.

    I’m going to pass on Tony’s advice, ” … a mistake to exclude the actual memorized “combination” as a component …”

    Quite frankly, I’m with Beldar on this one.

  4. Not only that but consider this Gene. A person gets nicked for sending a threatening message. The fact that the person used her fingerprint to unlock the phone 1 minute before the phone was dialed can be used against the defendant.

    Also, be something the government can use to track people as there is this hunger by the gov’t to get everyone’s prints on file it would surely be an easy way to watch everyone.

  5. I have a low res cheap phone and don’t own an iphone so take this for what it’s worth. I have seen where people look at a picture on the phone and touch certain locations on that picture in sequence and it unlocks the phone. I would say that would be protective of the 5th amendment due to the combination used.

    For fingerprint worries, I suppose one test it and see if the using the top of their index finger, that is the area between the knuckle below the nail and the second knuckle below that. Curl the finger to make a flat ridge and then see if that will work (the fingers are in the same position as if doing knuckle pushups) Gov’t and police agencies do not use the tops of fingers for printing or databasing. It might work, it might not, it’s going to have fewer points of identification though.

    Maybe if in using the standard finger print unlocker you can config the phone to accept three touches from different fingers in a certain order and therefore it would be the combination from the mind.

  6. And you really believe that, David?

    Given Apple’s “walled garden” approach to code, I don’t think I’m going to take them at their word on this matter. An ounce of prevention beats a pound of cure.

  7. David,
    Thanks for the update. But, couldn’t Apple provide the NSA a backdoor for the fingerprint information? We know the NSA has been “granted” enormous access by the telecoms. Why should anyone trust this?

  8. Nal,

    Glad you wrote about this subject. I had read an article about it this morning.


    Senator Concerned About Apple’s Fingerprint Tech
    NEW YORK September 20, 2013 (AP)
    By BREE FOWLER AP Technology Writer

    According to Apple, the fingerprint data is stored on the phone in a place that’s inaccessible to other apps and to Apple’s remote servers. Apple also has put in a number of safeguards, including requiring a passcode after a restart and 48 hours of inactivity. In addition, Apple says it’s not possible to take an existing fingerprint and convert it into something the phone will recognize, as the sensor reads a sub-epidermal layer of the finger.

    Joe Schumacher, security consultant at Neohapsis, said Apple’s fingerprint technology seems different and possibly more accurate than older readers, so most people shouldn’t need to worry. But he said it could still be “a risk for any possible targeted individual,” and much of the risk comes from not knowing many details.

    “There is a big security risk with Touch ID without explicit understanding of how Apple is handling this data from storage to sharing with other entities,” he said in a statement.

    Meanwhile, anyone worried about fingerprint scan has the option of disabling the feature and sticking with the passcode.

  9. Of course we have to be concerned that the Tim Cook response is true but if it is then we are all rushing to make connections and increase our well founded paranoia in areas where the paranoia may not yet be well founded.

  10. Do not buy, use or trust, any device which has a brand name which begins with first letter lower case and next letter upper case. It indicates that the seller or producer is from an alien planet. I do not know these things first hand because we are from France.

  11. Very timely! It will be interesting to see how quickly law enforcement jumps on this: and will that kill the technology? How soon will we be seeing YouTube video of police pushing handcuffed fingers onto iPhones?

  12. Raff,

    Sen. Al Franken questions Tim Cook on iPhone 5s fingerprint sensor privacy concerns:

    Touch ID does not store any images of your fingerprint. It stores only a mathematical representation of your fingerprint. It isn’t possible for your actual fingerprint image to be reverse-engineered from this mathematical representation. iPhone 5s also includes a new advanced security architecture called the Secure Enclave within the A7 chip, which was developed to protect passcode and fingerprint data. Fingerprint data is encrypted and protected with a key available only to the Secure Enclave. Fingerprint data is used only by the Secure Enclave to verify that your fingerprint matches the enrolled fingerprint data. The Secure Enclave is walled off from the rest of A7 and as well as the rest of iOS. Therefore, your fingerprint data is never accessed by iOS or other apps, never stored on Apple servers, and never backed up to iCloud or anywhere else. Only Touch ID uses it and it can’t be used to match against other fingerprint databases.

    Sounds good.

  13. CUT & PASTE Spying on Americans before 9/11: NSA Built Back Door In All Windows Software by 1999

    But according to two witnesses attending the conference, even Microsoft’s top crypto programmers were astonished to learn that the version of ADVAPI.DLL shipping with Windows 2000 contains not two, but three keys. Brian LaMachia, head of CAPI development at Microsoft was “stunned” to learn of these discoveries, by outsiders.

    Don’t doubt AT ALL that fingerprints would be sent to NSA as well….(no matter WHAT they claim)

  14. That was my thought Gene. If that is the case, the NSA would be able to not only obtain our phone calls, but access to any files on our phone. Explain to me again, why would I want the fingerprint authentication?

  15. David: Interesting, and something I did not know before.

    Certain pieces of my equipment and most of my accounts use pass phrases (or acronymical of pass phrases) that I have never spoken in public, and never will, since they will never arise in conversation. They are basically auto-biographical and memorable to me.

    So now I think it would be cool to couple that with a retinal or fingerprint or voice verification, but a mistake to exclude the actual memorized “combination” as a component.

  16. This is a bit disturbing, because it may be that fingerprinting technology is a more solid method for the identification of individuals, seeing as how genetic (DNA) identifications is likely to be under some long-term scientific scrutiny:

    From biology class to “C.S.I.,” we are told again and again that our genome is at the heart of our identity. Read the sequences in the chromosomes of a single cell, and learn everything about a person’s genetic information — or, as 23andme, a prominent genetic testing company, says on its Web site, “The more you know about your DNA, the more you know about yourself.”

    But scientists are discovering that — to a surprising degree — we contain genetic multitudes. Not long ago, researchers had thought it was rare for the cells in a single healthy person to differ genetically in a significant way. But scientists are finding that it’s quite common for an individual to have multiple genomes. Some people, for example, have groups of cells with mutations that are not found in the rest of the body. Some have genomes that came from other people.

    Medical researchers aren’t the only scientists interested in our multitudes of personal genomes. So are forensic scientists. When they attempt to identify criminals or murder victims by matching DNA, they want to avoid being misled by the variety of genomes inside a single person.

    Last year, for example, forensic scientists at the Washington State Patrol Crime Laboratory Division described how a saliva sample and a sperm sample from the same suspect in a sexual assault case didn’t match.

    (The “It’s In Your Genes” Myth – 2). Microbial genetic material makes up about 98% of the human microbiome, but little is known about microbes, in terms of cataloging that genetic material.

    There may be a serious problem with forensic practices that needs to be addressed.

    Since fingerprinting and voice may be more stable, perhaps that should be taken into consideration.

  17. Excellent topic, David. This story caught my eye this week as well. It was on my short list, however, I’ll settle for a “what you said” since you did such a fine job. 😀

    I would like to simply add the observation that as our machines become more sophisticated in how they interact with us and we with them that Locard’s Exchange Principle grows logarithmically.

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