Android Lollipop’s default encryption comes at a significant performance price
In software, very rarely is an operation “free.” Want that menu to have a cute scroll-down animation when you tap it? Sure, but that’s going to take up processor time: you can have a system without it that runs slightly faster, or keep the animation and suffer a tiny performance hit. Our desire for attractive, rich software is often compensated for by the arrival of increasingly powerful SoCs, but that still doesn’t change the fact that the more we ask our phone to do, the slower the same hardware’s going to run. With Android 5.0 Lollipop, Google is making its platform’s full-disk encryption enabled by default for new devices. Encryption sound good (so good that it’s making the government nervous), but what’s the cost for all this new data encryption and decryption taking place behind the scenes? An analysis prepared with a special unencrypted Nexus 6 suggests that it’s quite high.
Now, you can’t just turn off the encryption with a Nexus 6 or any other Android-5.0-out-of-the-box model: it’s permanently enabled. To see what extent the encryption was having on read/write speeds the team at AnandTech had Motorola send them a custom-configured Nexus 6 without any disk encryption at all – you can’t buy a Nexus 6 like this. And lo and behold: the commercial, fully-encrypted Nexus 6 showed a 50 to 80 percent drop in read/write performance compared to the unencrypted model.
But OK, so there’s a performance hit: at least you get extra security out of it. Well, maybe not so much. The encryption is tied to your lockscreen security, and if you choose not to use any lockscreen at all, you don’t just miss out on additional device protection, but the still-present encryption layer is eating up resources, slowing down your file access.
There’s work already underway at preparing alternate bootloaders for devices like the Nexus 6 that would let users who so choose fully disable the otherwise mandatory encryption.