Encryption certainly isn't the sexiest of topics for most people; we want our data to be secure from nefarious sorts and then move on. The challenge with encryption is that depending on the algorithm and type of encryption used, it can consume lots of system resources. This isn't such a big deal on high-end smartphones as many of them have special hardware to handle the encryption workload. It is a big deal on lower-end devices that have to do all the encryption work on the main SoC, and for those devices, it can mean poor performance and batteries that drain faster.
Google has a new mode of storage encryption called Adiantum that is made specifically for devices that lack the capacity to use AES due to slower SoCs. Google says that Adiantum allows it to use the ChaCha stream cipher in a length-preserving mode that adapts ideas from AES-based proposals for length-preserving encryption, such as HCTR and HCH.
Google gives an example of the gains that Adiantum will offer on devices running an ARM Cortex-A7. On a device with that SoC, Adiantum encryption and decryption is about 10.6 cycles per bytes, that is about five times faster than AES-256-XTS on the same device. Google also notes that while Adiantum is very new, it has high confidence in its security.
The overhead for the new encryption protocol is so low that it can be used on devices like smartwatches, TVs, and medical devices. Google is unclear when Adiantum will go into service and what devices will utilize the new protocol first. Google is working hard on increasing the performance of devices using its tech, recently details on Chrome Never-Slow mode surfaced hinting the new mode was coming to curtail the tendency of Chrome to consume all the system resources, slowing a device down.