  Disk encryption is frequently used to secure confidential data on mobile
devices. However, the high energy cost of disk encryption poses a heavy burden
on those devices with limited battery capacity especially when a large amount
of data needs to be protected by disk encryption. To address the challenge, we
develop a new kernel-level disk encryption software, Populus. Almost 98% of
Populus's encryption/decryption computation is not related with the input
plaintext/ciphertext, so we accomplish the computation in advance during
initialization when a consistent power supply is available. We conduct
cryptanalysis on Populus and finally conclude that state-of-the-art
cryptanalysis techniques fail to break Populus in reasonable computational
complexity. We also conduct energy consumption experiments on Populus and
dm-crypt, a famous disk encryption software for Android and Linux mobile
devices. The experimental results demonstrate that Populus consumes 50%-70%
less energy than dm-crypt.
