iOS on-disk file encryption questions
iOS on-disk file encryption questions
- Subject: iOS on-disk file encryption questions
- From: Jens Alfke <email@hidden>
- Date: Thu, 22 Dec 2011 16:52:33 -0800
There’s a brief description in the iOS docs of "Protecting Data Using On-Disk Encryption”. Unfortunately there’s no description of how the file encryption actually happens, so I’m unsure whether it’s suitable for use with database files that can grow large, are updated incrementally, and are accessed using low-level read/write calls instead of Cocoa APIs.
Basically there are two ways I can think of this being implemented:
(1) Encrypt individual blocks of the file as they’re written/read, and do the encryption at the filesystem level, beneath the read/write system calls.
or
(2) Decrypt the entire file into RAM when it’s opened, and write it back encrypted when it’s closed.
Approach (1) will work great with things like sqlite or CouchDB. Approach (2) definitely won’t.
Anyone know for sure, or have experience using this feature with structured files?
Also, anyone know what the name of the underlying extended attribute is, so I can set it from C code?
—Jens
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