Excellent advice. Even better, if you're about to pass through US customs and border patrol, backup the phone first, wipe, and restore on the other side. Of course, this depends on your level of paranoia. I am paranoid.
I recommend you make a backup to your laptop, which you then encrypt manually. That way the trust model is: you trust yourself. Then you can do whatever you want with the encrypted file. Apple's iCloud is perfectly fine at this point.
The real challenge is to find a way to restore that backup, because you have to be on a computer you trust. If you decrypt the backup on a "loaner" laptop, your security is broken.
If you decrypt the backup on your personal laptop but the laptop has a hidden keylogger installed by the TSA or TAO, your security is broken.
It would be necessary to backup the phone on the _phone_ _itself_. Then manually encrypt the file (easy to do). Then upload to iCloud. At this time, no such app exists for iOS.
Since you plan to restore the backup to the phone anyway, it's no problem to decrypt a file on the phone before using it for the restore.
You mean your laptop that was manufactured by a 3rd party, with a network card that was manufactured by a 3rd party? And you're using encryption software that, even if it's open source, you probably aren't qualified to code review. I'm not downplaying the benefit of being careful, but unfortunately you can keep doing that pretty much forever.
its not trivial, but its sure easy to do in this day and age.
And it's paranoia if there's a legitimate threat, that's just called due diligence. ;)
Do the docs confirm that there is no way around this? I'd guess generating the encryption key requires the passcode, which is discarded immediately, and Touch ID can only "unlock" a temporarily re-encrypted version which never leaves ephemeral storage?
If Touch ID is turned off, when a device locks, the keys for Data Protection class
Complete, which are held in the Secure Enclave, are discarded. The files and keychain
items in that class are inaccessible until the user unlocks the device by entering his
or her passcode.
With Touch ID turned on, the keys are not discarded when the device locks; instead,
they’re wrapped with a key that is given to the Touch ID subsystem inside the Secure
Enclave. When a user attempts to unlock the device, if Touch ID recognizes the user’s
fingerprint, it provides the key for unwrapping the Data Protection keys, and the
device is unlocked. This process provides additional protection by requiring the
Data Protection and Touch ID subsystems to cooperate in order to unlock the device.
The keys needed for Touch ID to unlock the device are lost if the device reboots
and are discarded by the Secure Enclave after 48 hours or five failed Touch ID
recognition attempts.Now Cydia and 3rd party stuff? I have no clue.
If I absolutely had to I just wouldn't take a phone/laptop with me.
I wonder if there is any negative effects associated with being refused entry by a CBP? Could it be the case that if you are refused entry once, that in the future they will be more likely to refuse you entry? If so, that's a fairly significant penalty/power that the CBP person has.