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.\" $FreeBSD$
.Dd June 6, 2004
.Dt MD5 1
.Os
.Sh NAME
.Nm md5 , sha1 , sha256, rmd160
.Nd calculate a message-digest fingerprint (checksum) for a file
.Sh SYNOPSIS
.Nm md5
.Op Fl pqrtx
.Op Fl s Ar string
.Op Ar
.Nm sha1
.Op Fl pqrtx
.Op Fl s Ar string
.Op Ar
.Nm sha256
.Op Fl pqrtx
.Op Fl s Ar string
.Op Ar
.Nm rmd160
.Op Fl pqrtx
.Op Fl s Ar string
.Op Ar
.Sh DESCRIPTION
The
.Nm md5 , sha1 , sha256
and
.Nm rmd160
utilities take as input a message of arbitrary length and produce as
output a
.Dq fingerprint
or
.Dq 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
.Tn MD5 , SHA-1 , SHA-256
and
.Tn RIPEMD-160
algorithms are intended for digital signature applications, where a
large file must be
.Dq compressed
in a secure manner before being encrypted with a private
(secret)
key under a public-key cryptosystem such as
.Tn RSA .
.Pp
.Tn MD5
has not yet (2001-09-03) been broken, but sufficient attacks have been
made that its security is in some doubt.
The attacks on
.Tn MD5
are in the nature of finding
.Dq collisions
\(em that is, multiple
inputs which hash to the same value; it is still unlikely for an attacker
to be able to determine the exact original input given a hash value.
.Pp
The following options may be used in any combination and must
precede any files named on the command line.
The hexadecimal checksum of each file listed on the command line is printed
after the options are processed.
.Bl -tag -width indent
.It Fl s Ar string
Print a checksum of the given
.Ar string .
.It Fl p
Echo stdin to stdout and append the checksum to stdout.
.It Fl q
Quiet mode - only the checksum is printed out.
Overrides the
.Fl r
option.
.It Fl r
Reverses the format of the output.
This helps with visual diffs.
Does nothing
when combined with the
.Fl ptx
options.
.It Fl t
Run a built-in time trial.
.It Fl x
Run a built-in test script.
.El
.Sh EXIT STATUS
The
.Nm md5 , sha1 , sha256
and
.Nm rmd160
utilities exit 0 on success,
and 1 if at least one of the input files could not be read.
.Sh SEE ALSO
.Xr cksum 1 ,
.Xr md5 3 ,
.Xr ripemd 3 ,
.Xr sha 3 ,
.Xr sha256 3
.Rs
.%A R. Rivest
.%T The MD5 Message-Digest Algorithm
.%O RFC1321
.Re
.Rs
.%A J. Burrows
.%T The Secure Hash Standard
.%O FIPS PUB 180-2
.Re
.Rs
.%A D. Eastlake and P. Jones
.%T US Secure Hash Algorithm 1
.%O RFC 3174
.Re
.Pp
RIPEMD-160 is part of the ISO draft standard
.Qq ISO/IEC DIS 10118-3
on dedicated hash functions.
.Pp
Secure Hash Standard (SHS):
.Pa http://csrc.nist.gov/cryptval/shs.html .
.Pp
The RIPEMD-160 page:
.Pa http://www.esat.kuleuven.ac.be/~bosselae/ripemd160.html .
.Sh ACKNOWLEDGMENTS
This program is placed in the public domain for free general use by
RSA Data Security.
.Pp
Support for SHA-1 and RIPEMD-160 has been added by
.An Oliver Eikemeier Aq eik@FreeBSD.org .
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