MD5(1)                  System General Commands Manual                  MD5(1)

NAME
     md5 - calculate a message-digest fingerprint (checksum) for a file

SYNOPSIS
     md5 [-pqrtx] [-s string] [file ...]

DESCRIPTION
     Md5 takes as input a message of arbitrary length and produces as output a
     128-bit ``fingerprint'' or ``message digest'' of the input.  It is con-
     jectured 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 ``compressed''
     in a secure manner before being encrypted with a private (secret) key
     under a public-key cryptosystem such as RSA.

     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 MD5 are in
     the nature of finding ``collisions'' -- 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.

     The following options may be used in any combination and must precede any
     files named on the command line.  The MD5 sum of each file listed on the
     command line is printed after the options are processed.

     -s string
             Print a checksum of the given string.

     -p      Echo stdin to stdout and appends the MD5 sum to stdout.

     -q      Quiet mode - only the MD5 sum is printed out.  Overrides the -r
             option.

     -r      Reverses the format of the output.  This helps with visual diffs.
             Does nothing when combined with the -ptx options.

     -t      Run a built-in time trial.

     -x      Run a built-in test script.

SEE ALSO
     cksum(1)

     R. Rivest, The MD5 Message-Digest Algorithm, RFC1321.

ACKNOWLEDGMENTS
     This program is placed in the public domain for free general use by RSA
     Data Security.

BSD                            February 14, 1994                           BSD