.\"	$OpenBSD: md5.1,v 1.17 2003/06/17 21:56:23 millert Exp $
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.\" Copyright (c) 2003 Todd C. Miller <Todd.Miller@courtesan.com>
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.\" Agency (DARPA) and Air Force Research Laboratory, Air Force
.\" Materiel Command, USAF, under agreement number F39502-99-1-0512.
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.Dd June 4, 2001
.Dt MD5 1
.Os
.Sh NAME
.Nm md5
.Nd calculate a message-digest fingerprint (checksum) for a file
.Sh SYNOPSIS
.Nm md5
.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 128-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 MD5
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 RMD-160 and SHA-1.
If no file is given, stdin is used.
.It Fl p
Echoes stdin to stdout and appends the
.Em MD5
sum to stdout.
.It Fl t
Runs a built-in time trial.
.It Fl x
Runs a built-in test script.
.El
.Pp
The MD5 sum of each file listed on the command line is printed after the
options are processed.
.Sh SEE ALSO
.Xr cksum 1 ,
.Xr rmd160 1 ,
.Xr sha1 1
.Pp
RFC 1321 describes in detail the MD2, MD4, and MD5 message-digest algorithms.