.\"	$OpenBSD: sha1.1,v 1.4 1998/01/02 07:04:24 deraadt Exp $
.\"
.Dd July 12, 1997
.Dt SHA1 1
.Os
.Sh NAME
.Nm sha1
.Nd "calculate a message-digest fingerprint (checksum) for a file"
.Sh SYNOPSIS
.Nm
.Op Fl ptx
.Op Fl s Ar string
.Op Ar file ...
.Sh DESCRIPTION
.Nm
takes as input a message of arbitrary length and produces
as output a 160-bit "fingerprint" or "message digest" of the input.
It is conjectured that it is computationally infeasible to produce
two messages having the same message digest, or to produce any
message having a given prespecified target message digest.
The
.Em SHA-1
algorithm is intended for digital signature applications, where a
large file must be "compressed" in a secure manner before being
encrypted with a private (secret) key under a public-key cryptosystem
such as
.Em RSA .
.Sh OPTIONS
The following four options may be used in any combination and must
precede any files named on the command line.  The SHA-1
sum of each file listed on the command line is printed after the options
are processed.
.Bl -tag -width Fl
.It Fl s Ar string
prints a checksum of the given
.Ar string .
.It Fl p
echos stdin to stdout and appends the
.Em SHA-1
sum to stdout.
.It Fl t
runs a built-in time trial.
.It Fl x
runs a built-in test script.
.El
.Sh SEE ALSO
.Xr cksum 1 ,
.Xr md5 1 ,
.Xr rmd160 1
.Pp
NIST FIPS PUB 180-1 describes the SHA-1 message-digest algorithm in detail.
.Sh ACKNOWLEDGEMENTS
This program is placed in the public domain for free general use by
RSA Data Security.