.Dd February 14, 1994
.Dt MD5 1
.Os
.Sh NAME
.Nm md5
.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 Ns Pq s
.Sh DESCRIPTION
.Nm
takes as input a message of arbitrary length and produces
as output a 128-bit
.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 MD5 algorithm is intended for digital signature applications, where a
large file must be
.Dq compressed
in a secure manner before being encrypted with a private
.Pq secret
key under a public-key cryptosystem such as
.Em RSA .
.Pp
The following four options may be used in any combination, except
that
.Ar filename Ns Pq s
must be the last objects on the command line.
.Bl -tag -width Fl
.It Fl s Ns Ar string
prints a checksum of the given
.Dq string .
.It Fl p
echos stdin to stdout and appends the MD5 sum to stdout.
.It Fl t
runs a built-in time trial.
.It Fl x
runs a built-in test script.
.It Ar filename Ns Pq s
prints a checksum
.Pq s
for each of the files.
.El
.Sh SEE ALSO
.Xr cksum 1
.Rs
.%A R. Rivest
.%T The MD5 Message-Digest Algorithm
.%O RFC1321
.Re
.Sh ACKNOWLEDGEMENTS
This program is placed in the public domain for free general use by
RSA Data Security.