Orin S. Kerr (University of Southern California Gould School of Law) has posted Compelled Decryption and the Privilege Against Self-Incrimination (Texas Law Review, Forthcoming) on SSRN. Here is the abstract:
This essay considers the Fifth Amendment barrier to orders compelling a suspect to enter in a password to decrypt a locked phone, computer, or file. It argues that a simple rule should apply: An assertion of privilege should be sustained unless the government can independently show that the suspect knows the password. The act of entering in a password is testimonial, but the only implied statement is that the suspect knows the password. When the government can prove this fact independently, the assertion is a foregone conclusion and the Fifth Amendment poses no bar to the enforcement of the order. This rule is both doctrinally correct and sensible policy. It properly reflects the distribution of government power in a digital age when nearly everyone is carrying a device that comes with an extraordinarily powerful lock.
Highly recommended.