text_cmds/md5/md5.1

   1 .\" $FreeBSD: src/sbin/md5/md5.1,v 1.24 2005/03/10 09:56:39 cperciva Exp $
   2 .Dd June 6, 2004
   3 .Dt MD5 1
   4 .Os
   5 .Sh NAME
   6 .Nm md5
   7 .Nd calculate a message-digest fingerprint (checksum) for a file
   8 .Sh SYNOPSIS
   9 .Nm md5
  10 .Op Fl pqrtx
  11 .Op Fl s Ar string
  12 .Op Ar
  13 .Sh DESCRIPTION
  14 The
  15 .Nm
  16 utility takes as input a message of arbitrary length and produces as
  17 output a
  18 .Dq fingerprint
  19 or
  20 .Dq message digest
  21 of the input.
  22 It is conjectured that it is computationally infeasible to
  23 produce two messages having the same message digest, or to produce any
  24 message having a given prespecified target message digest.
  25 The
  26 .Tn MD5
  27 algorithm is intended for digital signature applications, where a
  28 large file must be
  29 .Dq compressed
  30 in a secure manner before being encrypted with a private
  31 (secret)
  32 key under a public-key cryptosystem such as
  33 .Tn RSA .
  34 .Pp
  35 .Tn MD5's
  36 designer Ron Rivest has stated "md5 and sha1 are both clearly broken (in terms
  37 of collision-resistance)".
  38 So
  39 .Tn MD5
  40 should be avoided when creating new protocols, or implementing protocols with better options.
  41 .Tn SHA256
  42 and
  43 .Tn SHA512
  44 are better options as they have been more resilient to attacks (as of 2009).
  45 .Pp
  46 The following options may be used in any combination and must
  47 precede any files named on the command line.
  48 The hexadecimal checksum of each file listed on the command line is printed
  49 after the options are processed.
  50 .Bl -tag -width indent
  51 .It Fl s Ar string
  52 Print a checksum of the given
  53 .Ar string .
  54 .It Fl p
  55 Echo stdin to stdout and append the checksum to stdout.
  56 .It Fl q
  57 Quiet mode - only the checksum is printed out.
  58 Overrides the
  59 .Fl r
  60 option.
  61 .It Fl r
  62 Reverses the format of the output.
  63 This helps with visual diffs.
  64 Does nothing
  65 when combined with the
  66 .Fl ptx
  67 options.
  68 .It Fl t
  69 Run a built-in time trial.
  70 .It Fl x
  71 Run a built-in test script.
  72 .El
  73 .Sh EXIT STATUS
  74 The
  75 .Nm
  76 utility exits 0 on success,
  77 and 1 if at least one of the input files could not be read.
  78 .Sh SEE ALSO
  79 .Xr cksum 1 ,
  80 .Xr md5 3 ,
  81 .Xr ripemd 3 ,
  82 .Xr sha 3 ,
  83 .Xr CC_SHA256_Init 3
  84 .Rs
  85 .%A R. Rivest
  86 .%T The MD5 Message-Digest Algorithm
  87 .%O RFC1321
  88 .Rs
  89 .%A Vlastimil Klima
  90 .%T Finding MD5 Collisions - a Toy For a Notebook
  91 .%O Cryptology ePrint Archive: Report 2005/075
  92 .Re
  93 .Sh ACKNOWLEDGMENTS
  94 This program is placed in the public domain for free general use by
  95 RSA Data Security.