This library and command line tool were designed as near drop-in
replacements for common SHA-1 libraries and sha1sum. They will compute
the SHA-1 hash of any given file and additionally will detect
cryptanalytic collision attacks against SHA-1 present in each file.
It is very fast and takes less than twice the amount of time as
regular SHA-1.

There are two programs:  sha1dcsum and sha1dcsum_partialcoll.
The first program, sha1dcsum, will detect and warn for files that were
generated with a cryptanalytic SHA-1 collision attack like the one
documented at https://shattered.io/. The second program,
sha1dcsum_partialcoll, will detect and warn for files that were
generated with a cryptanalytic collision attack against reduced-
round SHA-1 (of which there are a few examples so far).