Android 5.0 Lollipop’s Encryption Significantly Slows Memory Access on the Nexus 6

November 20, 2014 - Written By David Steele

Security should be at the forefront of our minds when using our portable devices, because these Android devices often go anywhere with us and are easily stolen. I’m sure that all of my readers have a lock code, PIN, password or similar set up and you may have seen some of the improvements built into Android Lollipop. One key advantage is that the device if encrypted as standard, which ensures that should the device be stolen, the thief cannot easily access your days without the code. Another part of Android 5.0 Lollipop‘s security is the smart unlocking features, which makes it easy and fast to unlock the device. After all, if a security feature is difficult or awkward to use, it’s not going to get used!

And this being me to the point of my article: the device encryption built into Android Lollipop has a performance hit. The Nexus 6 uses a technology called Full Disk Encryption, or FDE, whereby every piece of data read from storage needs to be decrypted and every piece of data written to internal storage needs to be encrypted. This encryption process for the Nexus 6 relies on the processor and is not supported by the storage unit itself (or by a specialist core on the processor). AnandTech recently posted a comparison of the storage of a Nexus 6 running the stock, encrypted ROM and one with the encryption removed by Motorola. The results, courtesy of AnandTech, are showing at the bottom of my post, show a significant performance penalty associated with the Nexus 6’s encryption. Random read performance is some 63% slower, random write performance is 50% slower and sequential read performance is over 80% slower.

What does this mean? It means that when you are using a device with Android Lollipop’s FDE activated, the device is not running as fast as with it turned off. Things are worse if you are using the device without a passcode as you still suffer the performance penalty but don’t have the benefit of the improved security. That the Nexus 6 and Nexus 9 have FDE activated as standard means that many users won’t notice the difference in performance, especially if they’re moving from a slower device, but once we’ve seen these statistics, they cannot be unseen! The geeks among us will lament the performance hit! On a more serious note, it’s great that Google have enabled the encryption but it seems technology still has a way to go to keep up. However, it appears that any of the small performance hiccups people have noticed with the Nexus 6 and 9 don’t appear to be associated with sluggish memory storage as AnandTech didn’t notice any difference when using the unencrypted Nexus 6. Let’s hope that Google improve the performance of their FDE. And perhaps going forward the chipset manufacturers will work on integrating encryption cores into their designs?

nexus 6 encryption speeds