.Dd February 20, 2016
.Dt B2SUM 1
.Os
.Sh NAME
.Nm b2sum
.Nd generate checksums using the BLAKE2 hash function
.Sh SYNOPSIS
.Nm
.Op Fl a Ar algorithm
.Op Fl l Ar length
.Op Fl -tag
.Op Ar file ...
.Nm
.Op Fl -help
.Sh DESCRIPTION
The
.Nm
command generates checksums for files using the BLAKE2 cryptographic
hash function and writes them to standard output.
.Pp
When
.Op Ar file ...
is empty or -,
.Nm
reads from standard input.
.Bl -tag -width Ar
.It Fl a Ar algorithm
Specify a variant of BLAKE2 to use when generating checksums. The
variants are listed under the algorithms section, and the default
is blake2b.
.It Fl l Ar length
Specify the digest length in bits. It must not exceed the maximum
for the variant of BLAKE2 being used, and must be a multiple of 8.
.It Fl -tag
Prepend the checksums with
.Qq "ALGORITHM-NAME (file) =" ,
a format common on BSD systems.
.It Fl -help
Display usage.
.El
.Sh ALGORITHMS
.Bl -tag -width blake2xx
.It blake2b
optimized for 64-bit platforms and NEON-enabled ARMs, produces digests
of any size between 1 and 64 bytes
.It blake2s
optimized for 8 to 32-bit platforms, produces digests of any size
between 1 and 32 bytes
.It blake2bp
4-way parallel BLAKE2b
.It blake2sp
8-way parallel BLAKE2s
.El
.Sh SEE ALSO
.Xr shasum 1
.Sh STANDARDS
.Bl -tag -width "RFC XXXX"
.It RFC 7693
The BLAKE2 Cryptographic Hash and Message Authentication Code
.El
.Sh AUTHORS
.Nm
is part of the
.Em BLAKE2
official implementation. BLAKE2 was designed by
.An -nosplit
.An "Jean-Philippe Aumasson" ,
.An "Samuel Neves" ,
.An "Zooko Wilcox-O'Hearn" , and
.An "Christian Winnerlein" .
.Pp
BLAKE2 is based on the SHA-3 proposal
.Em BLAKE
which was designed by
.An "Jean-Philippe Aumasson" ,
.An "Luca Henzen" ,
.An "Willi Meier" , and
.An "Raphael C.-W. Phan" .
.Pp
BLAKE2, like BLAKE, relies on the
.Em ChaCha20
stream cipher, designed by
.An Daniel J. Bernstein .
.Pp
A mailing list for BLAKE2 can be subscribed to by sending an empty
message to
.Mt info-subscribe@blake2.net .
.Pp
The four designers of BLAKE2 can be contacted at
.Mt contact@blake2.net .
.Pp
This manual page was written by
.Lk https://github.com/Scarletts Scarlett .