No releases since May 2016, no commits since September 2016, with
62 open issues and 37 open PRs.
Author is unresponsive:
https://github.com/DaGenix/rust-crypto/issues/440
Advisory includes a large list of maintained "successor" crates:
`rust-crypto` was a kitchen sink of functionality, so the advisory
contains a list of potential successor crates each with an
algorithm-by-algorithm breakdown of what they support.