Biometric Passcodes and the Ease of Forced Decryption

-- By KyungjinKim - 11 Mar 2022

Introduction

Since 2013, when Apple introduced "the first major smartphone to feature a fingerprint scanner," biometric passcodes have exploded in popularity. Biometric passcodes - passcodes utilizing fingerprint or facial recognition technology to unlock devices - are now enabled on more than 71% of all mobile phones. Even while ignoring the numerous security risks in the software, the 85% of Americans who own a smartphone should be worried about the ease with which law enforcement can unlock their smartphones. While law enforcement can only enter alphanumerical passcodes with the users' voluntary cooperation, law enforcement can enter in biometric passcodes through "forced decryption" - pressing the user's fingers on the home button or holding the phone to the user's face. Faced with this possibility, users may believe that there are Constitutional limits against forced decryption, either because people have the right right "to be secure in their persons," or because people cannot be "compelled in any criminal case to be a witness against himself." However, existing caselaw casts serious doubts as to whether either Amendment can offer sufficient protection.

Fourth Amendment Protections

In Riley, the Supreme Court held that the Fourth Amendment does not provide absolute protection from all searches of smartphone data; rather, the Court only held that a warrant is generally required before such a search. Riley v. California, 573 U.S. 373, 401 (2014). Because the Fourth Amendment allows a warrant to be issued upon "probable cause," the subsequent question is ""[w]hat level of cause... the government might need to seize the suspect to enable the biometric access?"

The Fourth Amendment and caselaw agrees that, in a scenario in which 1) the particular devices are specified, 2) the user is specified, 3) there is probable cause for searching the device, and 4) there is probable cause for believing the device belongs to the defendant, the Fourth Amendment requirements are satisfied for biometric forced decryption purposes. See, e.g., United States v. Barrera, 415 F. Supp. 3d 832 (N.D. Ill. 2019). However, while most courts seem to agree that (3) is necessary, they remain heavily split for cases when (1) and (4) are not satisfied. On one hand, some courts have held that a warrant that was not limited to a particular person or a particular device did not demonstrate probable cause for Fourth Amendment purposes. In re Search of a Residence in Oakland, 354 F. Supp. 3d 1010 (N.D. Cal. 2019); In re Application for a Search Warrant, 236 F. Supp. 3d 1066 (N.D. Ill. 2017). On the other hand, some district courts have held that Fourth Amendment requirements were met as long as the procedure was carried out with dispatch in the immediate vicinity of the premises to be searched, the government has reasonable suspicion that the suspect has committed a criminal act that is the subject matter of the warrant, and the government has reasonable supicion that the individual's biometric features will unlock the device. In re Search of, 317 F. Supp. 3d 523, 532-33 (D.D.C. 2018); In re Search Warrant No. 5165, 470 F. Supp. 3d 715, 724 (E.D. Ky. 2020). Consequently, the worst case scenario is that a user will be legally compelled to unlock their devices simply for being near the premises of a searched area.

Fifth Amendment Protections

However, users may find refuge under the Fifth Amendment, if forced decryption is fond to be an act which compel the user to be a witness against himself. Generally, the question is whether providing the biometric passcode is 1) a communication or a communicative act that is 2) testimonial, 3) incriminating and 4) compelled." Barrera , at 835 (N.D. Ill. 2019) (citing Fisher v. United States, 425 U.S. 391, 408 (1976)). For there to be Fifth Amendment protection, all four criterion must be satisfied. However, courts remain divided concerning all the factors. To begin with, some courts hold that providing a biometric passcode is not a communicative act at all, and merely a physical act. In re Search Warrant Application, 279 F. Supp. 3d 800 (N.D. Ill. 2017); In re Search of, 317 F. Supp. 3d 523 (D.D.C. 2018). Courts that hold the provision is a communicative act agree that the provision is incriminating and compelled. However, they are heavily split on whether it is testimonial. Some of the courts have held that, because the biometric key is provision of a physical characteristic and not a communicative testimony, the act is not testimonial. State v. Diamond, 905 N.W.2d 870 (Minn. 2018); Barrera ; In re search of A White Google Pixel 3 Xl Cellphone in a Black Incipio Case, 398 F. Supp. 3d 785 (D. Idaho 2019). Finally, some courts have held that because provision of the key is implicit of the fact that the user owns or controls the content of the phone, the act is testimonial. In re Application for a Search Warrant, 236 F. Supp. 3d 1066 (N.D. Ill. 2017); In re Search of a Residence in Oakland, 354 F. Supp. 3d 1010 (N.D. Cal. 2019). Thus, a user can only depend on their jurisdiction's interpretation, and not the Fifth Amendment itself, for Constitutional protections against forced decryption.

Conclusion

At this point, a user may wonder whether the exclusive use of alphanumerical passcodes is a preferable option over biometric passcodes. While users cannot be forced to testify about their alphanumerical passcodes, due to Fifth Amendment protections, the protection does not extend to warrants or court orders authorizing the users to present a decrypted version of the files on the device. Courts and academics agree that when the government can provide independent evidence that certain files exist on the encrypted portion of the devices and the defendant can access them, there is no Fifth Amendment protection against a decryption order. Some academics have even argued that the government only needs to demonstrate independent knowledge that the person has the passcode. In any case, given the low amount of Constitutional protections some courts have held for biometric protection, an average user may be better off only using alphanumerical passcodes.

This draft accurately summarizes the uncertain state of Fourth Amendment law in the absence of some overarching Supreme Court opinion that would set lower court direction for decades. All of this could have been put in one paragraph, however. Biometric identification is always a bad idea. Any credentials that can never be changed and that are necessarily reused in multiple contexts are poorly designed, to say the least. So it makes not the slightest difference what the legal rules are in deciding whether to use utterly flawed and ultimately self-harming technology. Explaining that clearly would be worth far more to the reader than a rehash of the "don't know, probably doesn't matter" reflection on this one facet of the general 4th amendment failure I spent weeks describing.

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