This is fsverity, a userspace utility for fs-verity.
fs-verity is a Linux kernel feature that does transparent on-demand
integrity/authenticity verification of the contents of read-only files,
using a hidden Merkle tree (hash tree) associated with the file.
The mechanism is similar to dm-verity, but implemented at the file level
rather than at the block device level. The fsverity utility allows you
to set up fs-verity protected files.
