Eric Biggers and Paul Crowley were unhappy with the disk encryption options available for Android on low-end phones and watches. For them, it was an ethical issue. Eric said:
We believe encryption is for everyone, not just those who can afford it. And while it’s unknown how long CPUs without AES support will be around, there will likely always be a “low end”; and in any case, it’s immensely valuable to provide a software-optimized cipher that doesn’t depend on hardware support. Lack of hardware support should not be an excuse for no encryption.
Unfortunately, they were not able to find any existing encryption algorithm that was both fast and secure, and that would work with existing Linux kernel infrastructure. They, therefore, designed the Adiantum encryption mode, which they described in a light, easy-to-read and completely non-mathematical way.
Read more at Linux Journal