.\"	$OpenBSD: sha1.1,v 1.14 2003/03/14 09:59:20 jmc Exp $
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.\" Copyright (c) 2003 Todd C. Miller <Todd.Miller@courtesan.com>
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.Dd June 4, 2001
.Dt SHA1 1
.Os
.Sh NAME
.Nm sha1
.Nd calculate a message-digest fingerprint (checksum) for a file
.Sh SYNOPSIS
.Nm sha1
.Oo
.Fl p | Fl t | Fl x |
.Fl s Ar string |
.Fl c Ar [ file ... ] |
.Ar file ...
.Oc
.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.
.Pp
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 .
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl s Ar string
Prints a checksum of the given
.Ar string .
.It Fl c Ar [ file ... ]
Compares all checksums in
.Ar file
with newly computed checksums for the files mentioned in
.Ar file .
Output consists of the digest used, the file name,
and an OK or FAILED for the result of the comparison.
This will validate any of the supported checksums in
.Ar file ,
including MD5 and RMD-160.
If no file is given, stdin is used.
.It Fl p
Echoes 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
.Pp
The SHA-1
sum of each file listed on the command line is printed after the options
are processed.
.Sh SEE ALSO
.Xr cksum 1 ,
.Xr md5 1 ,
.Xr rmd160 1
.Rs
.%A J. Burrows
.%T The Secure Hash Standard
.%O FIPS PUB 180-1
.Re
.Rs
.%A D. Eastlake and P. Jones
.%T US Secure Hash Algorithm 1
.%O RFC 3174
.Re