- hardware key storage, iphone/TPM style
- mechanism for the manufacturer to authorise key release from a device
- important 1: this process should be irreversibly tamper-evident, such as IC "fuses" or one-time PROM. This should be permanently visible in the UI, so it cannot be applied invisibly.
- important 2: an obligation on the state to pay for replacement devices which have been compromised in the previous step but not used in court. This is to prevent it being routineised.
If nobody but me has the device encryption key, and my device is stolen, I can be sure that nobody will have access to whatever data it contains. If anybody else has the device encryption key, however, and the device is stolen, I can no longer know whether anybody else had access to the data, no matter how much tamper evidence the device has.
If we accept that mechanisms in common use, like warrantful search of physical belongings under the Fourth Amendment of the US Constitution, are legitimate and rightful functions of government, then warrantful key disclosure is a logical compromise that protects the individual's privacy, except when the government compels them with good cause to reveal information. Balancing this with protections against self-incrimination is one complication that's currently playing out.