md5 -- calculate a message-digest fingerprint (checksum) for a file
md5 [-pqrtx] [-s string] [file ...]
The md5 utility 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. 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.
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
-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.
The md5 program exits 0 on success, and 1 if at least one of the input
files could not be read.
R. Rivest, The MD5 Message-Digest Algorithm, RFC1321.
This program is placed in the public domain for free general use by RSA
FreeBSD 5.2.1 February 14, 1994 FreeBSD 5.2.1 [ Back ]