sha256(n) SHA-x Message-Digest Algorithm sha256(n) 







sha256 - SHA256 Message-Digest Algorithm








package require Tcl 8.2


package require sha256 ?1.0.3?


::sha2::sha256 ?-hex|-bin? [ -channel channel
    | -file filename | string ]


::sha2::sha224 ?-hex|-bin? [ -channel channel
    | -file filename | string ]


::sha2::hmac key string


::sha2::hmac ?-hex|-bin? -key key [
    -channel channel | -file filename | string ]


::sha2::SHA256Init


::sha2::SHA224Init


::sha2::SHA256Update token data


::sha2::SHA256Final token


::sha2::SHA224Final token


::sha2::HMACInit key


::sha2::HMACUpdate token data


::sha2::HMACFinal token












This package provides an implementation in Tcl of the SHA256 and
    SHA224 message-digest algorithms as specified by FIPS PUB 180-1 (1). These
    algorithms take a message and generates a 256-bit (224-bit) digest from the
    input. The SHA2 algorithms are related to the SHA1 algorithm.


This package also includes support for creating keyed
    message-digests using the HMAC algorithm from RFC 2104 (3) with SHA256 as
    the message-digest.









  
::sha2::sha256 ?-hex|-bin? [ -channel channel |
    -file filename | string ]

  
The command takes a message and returns the SHA256 digest of this message
      as a hexadecimal string. You may request the result as binary data by
      giving -bin.
    
The data to be hashed can be specified either as a string
        argument to the sha256 command, or as a filename or a pre-opened
        channel. 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. NOTE use of the
        channel or filename options results in the internal use of vwait.
        To avoid nested event loops in Tk or tclhttpd applications you should
        use the incremental programming API (see below).

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

  

  
::sha2::sha224 ?-hex|-bin? [ -channel channel |
    -file filename | string ]

  
Like ::sha2::sha256, except that the SHA224 digest is
    returned.

  
::sha2::hmac key string

  

  
::sha2::hmac ?-hex|-bin? -key key [ -channel
    channel | -file filename | string ]

  
Calculate an Hashed Message Authentication digest (HMAC) using the SHA256
      digest algorithm. HMACs are described in RFC 2104 (3) and provide an
      SHA256 digest that includes a key. All options other than -key are
      as for the ::sha2::sha256 command.










For the programmer, the SHA256 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 SHA256 hash operates on a token (equivalent to the bucket).
    You call SHA256Init to obtain a token and then call
    SHA256Update as many times as required to add data to the hash. To
    release any resources and obtain the hash value, you then call
    SHA256Final. An equivalent set of functions gives you a keyed digest
    (HMAC).


If you have critcl and have built the tcllibc
    package then the implementation of the hashing function will be performed by
    compiled code. Failing that there is a pure-tcl equivalent. The programming
    interface remains the same in all cases.



  
::sha2::SHA256Init

  

  
::sha2::SHA224Init

  
Begins a new SHA256/SHA224 hash. Returns a token ID that must be used for
      the remaining functions.

  
::sha2::SHA256Update token data

  
Add data to the hash identified by token. Calling SHA256Update $token
      "abcd" is equivalent to calling SHA256Update $token
      "ab" followed by SHA256Update $token "cb".
      See EXAMPLES. Note that this command is used for both SHA256 and
      SHA224. Only the initialization and finalization commands of both hashes
      differ.

  
::sha2::SHA256Final token

  

  
::sha2::SHA224Final 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 32/28 bytes representing the 256/224 bit SHA256 / SHA224 digest
      value.

  
::sha2::HMACInit key

  
This is equivalent to the ::sha2::SHA256Init command except that it
      requires the key that will be included in the HMAC.

  
::sha2::HMACUpdate token data

  

  
::sha2::HMACFinal token

  
These commands are identical to the SHA256 equivalent commands.










% sha2::sha256 "Tcl does SHA256"
0b91043ee484abd83c3e4b08d6034d71b937026379f0f59bda6e625e6e214789



% sha2::hmac Sekret "Tcl does SHA256"
4f9352c64d655e8a36abe73e6163a9d7a54039877c1c92ec90b07d48d4e854e0



% set tok [sha2::SHA256Init]
::sha2::1
% sha2::SHA256Update $tok "Tcl "
% sha2::SHA256Update $tok "does "
% sha2::SHA256Update $tok "SHA256"
% sha2::Hex [sha2::SHA256Final $tok]
0b91043ee484abd83c3e4b08d6034d71b937026379f0f59bda6e625e6e214789










  
[1]

  
"Secure Hash Standard", National Institute of Standards and
      Technology, U.S. Department Of Commerce, April 1995.
      (http://www.itl.nist.gov/fipspubs/fip180-1.htm)

  
[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)










This document, and the package it describes, will undoubtedly
    contain bugs and other problems. Please report such in the category
    sha1 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.








md4, md5, ripemd128, ripemd160, sha1








FIPS 180-1, hashing, message-digest, rfc 2104, security,
  sha256








Hashes, checksums, and encryption








Copyright (c) 2008, Andreas Kupries <andreas_kupries@users.sourceforge.net>








  

    1.0.3
    sha1