On Mon, Aug 21, 2017 at 09:44:11PM +0800, Anand Jain wrote: > > > > +fscrypt is not guaranteed to protect confidentiality or authenticity > > +if an attacker is able to manipulate the filesystem offline prior to > > +an authorized user later accessing the filesystem. > > How does fscrypt / Android protect against Evil Maid attack. ? In order to answer that question it's important to be specific about threat model is like; exactly what powers does the Evil Maid actually have? One of the stronger form of the Evil Maid attack posits that the Evil Made can remove the device from your hotel room, modify the hardware undetectably (up to and including desoldering the flash chip so it can be read and write directly), then replace it back to your hotel room, wait for you to login, and then later on, steal your phone and desolder the flash chip again. This sort of attack is going to require a combination of hardware and software features. Without talking about future product features on any specific future device being shipped by Google or any other company --- theoretically, if the keys are stored a hardware device which only disgorges the keys sends them directly to the in-line crypto engine without letting the keys be visible to the Linux kernel (or the Host CPU in any way at all), then it makes these sorts of Evil Maid much more difficult. Of course, if the Evil Maid can somehow insert something to tap the communications channel between the key storage device and the inline-crypto engine, then all bets are off. Presumably, though, this could be made harder; for example, by putting them on the system-on-a-chip. - Ted
