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.\" $OpenBSD: sha1.1,v 1.2 1997/07/12 21:26:58 millert 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 p
.Op Fl t
.Op Fl x
.Op Fl s Ns Ar string
.Op Ar filename(s)
.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, except
that
.Ar filename(s)
must be the last objects on the command line.
.Bl -tag -width "filename(s)"
.It Fl s Ns Ar string
prints a checksum of the given 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.
.It Ar filename(s)
prints the checksum for each file. If no files are specified,
standard input is used.
.El
.Sh SEE ALSO
.Xr cksum 1 ,
.Xr md5 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.
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