


md5(n)             MD5 Message-Digest Algorithm            md5(n)


______________________________________________________________________________

NAME
       md5 - MD5 Message-Digest Algorithm

SYNOPSIS
       package require Tcl  8.2

       package require md5  ?2.0.7?

       ::md5::md5 ?-hex? [ -channel channel | -file filename | string ]

       ::md5::hmac  ?-hex?  -key  key  [  -channel  channel | -file filename |
       string ]

       ::md5::MD5Init

       ::md5::MD5Update token data

       ::md5::MD5Final token

       ::md5::HMACInit key

       ::md5::HMACUpdate token data

       ::md5::HMACFinal token

_________________________________________________________________

DESCRIPTION
       This package is an implementation in  Tcl  of  the  MD5  message-digest
       algorithm  as  described in RFC 1321 (1). This algorithm takes an arbi-
       trary quantity of data and generates a 128-bit message digest from  the
       input.  The  MD5  algorithm is related to the MD4 algorithm (2) but has
       been strengthened against certain types of potential attack. MD5 should
       be used in preference to MD4 for new applications.

       If  you  have critcl and have built the tcllibc package then the imple-
       mentation of the hashing function will be performed by  compiled  code.
       Alternatively  if  you have either cryptkit or Trf then either of these
       can be used to accelerate the digest computation. If no  suitable  com-
       piled  package  is  available  then  the pure-Tcl implementation wil be
       used. The programming interface remains the same in all cases.

       Note the previous version of this package always returned a hex encoded
       string. This has been changed to simplify the programming interface and
       to make this version more compatible  with  other  implementations.  To
       obtain  the previous usage, either explicitly specify package version 1
       or use the -hex option to the md5 command.

COMMANDS
       ::md5::md5 ?-hex? [ -channel channel | -file filename | string ]
              Calculate the MD5 digest of the data given in  string.  This  is
              returned  as  a binary string by default. Giving the -hex option



md5                           2.0.7                             1





md5(n)             MD5 Message-Digest Algorithm            md5(n)


              will return a hexadecimal encoded version of the digest.

              The data to be hashed can be specified either as a string  argu-
              ment  to the md5 command, or as a filename or a pre-opened chan-
              nel. If the -filename argument is given then the file is opened,
              the data read and hashed and the file is closed. If the -channel
              argument is given then data is read from the channel  until  the
              end of file. The channel is not closed.

              Only one of -file, -channel or string should be given.

       ::md5::hmac ?-hex? -key key [ -channel channel | -file filename |
       string ]
              Calculate an Hashed Message Authentication digest  (HMAC)  using
              the  MD5  digest  algorithm. HMACs are described in RFC 2104 (3)
              and provide an MD5 digest that includes a key. All options other
              than -key are as for the ::md5::md5 command.


PROGRAMMING INTERFACE
       For  the  programmer, the MD5 hash can be viewed as a bucket into which
       one pours data. When you have finished, you extract  a  value  that  is
       derived  from the data that was poured into the bucket. The programming
       interface to the MD5 hash  operates  on  a  token  (equivalent  to  the
       bucket).  You call MD5Init to obtain a token and then call MD5Update as
       many times as required  to  add  data  to  the  hash.  To  release  any
       resources and obtain the hash value, you then call MD5Final. An equiva-
       lent set of functions gives you a keyed digest (HMAC).

       ::md5::MD5Init
              Begins a new MD5 hash. Returns a token ID that must be used  for
              the remaining functions.

       ::md5::MD5Update token data
              Add  data  to  the  hash  identified by token. Calling MD5Update
              $token "abcd" is equivalent to  calling  MD5Update  $token  "ab"
              followed by MD5Update $token "cb". See EXAMPLES.

       ::md5::MD5Final token
              Returns  the  hash value and releases any resources held by this
              token. Once this command completes the token  will  be  invalid.
              The  result  is a binary string of 16 bytes representing the 128
              bit MD5 digest value.

       ::md5::HMACInit key
              This is equivalent to the ::md5::MD5Init command except that  it
              requires the key that will be included in the HMAC.

       ::md5::HMACUpdate token data

       ::md5::HMACFinal token
              These commands are identical to the MD5 equivalent commands.





md5                           2.0.7                             2





md5(n)             MD5 Message-Digest Algorithm            md5(n)


EXAMPLES
       % md5::md5 -hex "Tcl does MD5"
       8AAC1EE01E20BB347104FABB90310433


       % md5::hmac -hex -key Sekret "Tcl does MD5"
       35BBA244FD56D3EDF5F3C47474DACB5D


       % set tok [md5::MD5Init]
       ::md5::1
       % md5::MD5Update $tok "Tcl "
       % md5::MD5Update $tok "does "
       % md5::MD5Update $tok "MD5"
       % md5::Hex [md5::MD5Final $tok]
       8AAC1EE01E20BB347104FABB90310433


REFERENCES
       [1]    Rivest,  R.,  "The  MD5 Message-Digest Algorithm", RFC 1321, MIT
              and RSA Data Security, Inc,  April  1992.   (http://www.rfc-edi-
              tor.org/rfc/rfc1321.txt)

       [2]    Rivest,  R.,  "The MD4 Message Digest Algorithm", RFC 1320, MIT,
              April 1992. (http://www.rfc-editor.org/rfc/rfc1320.txt)

       [3]    Krawczyk, H., Bellare, M. and Canetti, R.  "HMAC:  Keyed-Hashing
              for   Message   Authentication",   RFC   2104,   February  1997.
              (http://www.rfc-editor.org/rfc/rfc2104.txt)


BUGS, IDEAS, FEEDBACK
       This document, and the package it describes, will  undoubtedly  contain
       bugs and other problems.  Please report such in the category md5 of the
       Tcllib  SF  Trackers  [http://sourceforge.net/tracker/?group_id=12883].
       Please  also  report any ideas for enhancements you may have for either
       package and/or documentation.

SEE ALSO
       md4, sha1

KEYWORDS
       hashing, md5, message-digest, rfc 1320, rfc 1321, rfc 2104, security

CATEGORY
       Hashes, checksums, and encryption

COPYRIGHT
       Copyright (c) 2003, Pat Thoyts <patthoyts@users.sourceforge.net>








md5                           2.0.7                             3


