synopsis: Fast, pure and practical SHA-1 implementation
description: {
A practical incremental and one-pass, pure API to
the [SHA-1 cryptographic hash algorithm](https://en.wikipedia.org/wiki/SHA-1) according
to [FIPS 180-4](http://dx.doi.org/10.6028/NIST.FIPS.180-4)
with performance close to the fastest implementations available in other languages.
.
The core SHA-1 algorithm is implemented in C and is thus expected
to be as fast as the standard [sha1sum(1) tool](https://linux.die.net/man/1/sha1sum).
(If, instead, you require a pure Haskell implementation and performance is secondary, please refer to the [SHA package](https://hackage.haskell.org/package/SHA).)
conforming to [RFC6234](https://tools.ietf.org/html/rfc6234), [RFC4231](https://tools.ietf.org/html/rfc4231), [RFC5869](https://tools.ietf.org/html/rfc5869), et al..
=== Relationship to the @cryptohash@ package and its API
.
This package has been originally a fork of @cryptohash-0.11.7@ because the @cryptohash@
package had been deprecated and so this package continues to satisfy the need for a
lightweight package providing the SHA-1 hash algorithm without any dependencies on packages
other than @base@ and @bytestring@. The API exposed by @cryptohash-sha1-0.11.*@'s
"Crypto.Hash.SHA1" module is guaranteed to remain a compatible superset of the API provided
by the @cryptohash-0.11.7@'s module of the same name.
.
Consequently, this package is designed to be used as a drop-in replacement for @cryptohash-0.11.7@'s
"Crypto.Hash.SHA1" module, though with
a [clearly smaller footprint by almost 3 orders of magnitude](https://www.reddit.com/r/haskell/comments/5lxv75/psa_please_use_unique_module_names_when_uploading/dbzegx3/).
