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sha1(n)                                SHA-x Message-Digest Algorithm                                sha1(n)



____________________________________________________________________________________________________________

NAME
       sha1 - SHA1 Message-Digest Algorithm

SYNOPSIS
       package require Tcl  8.2

       package require sha1  ?2.0.3?

       ::sha1::sha1 ?-hex|-bin? [ -channel channel | -file filename | string ]

       ::sha1::hmac key string

       ::sha1::hmac ?-hex|-bin? -key key [ -channel channel | -file filename | string ]

       ::sha1::SHA1Init

       ::sha1::SHA1Update token data

       ::sha1::SHA1Final token

       ::sha1::HMACInit key

       ::sha1::HMACUpdate token data

       ::sha1::HMACFinal token

____________________________________________________________________________________________________________

DESCRIPTION
       This  package  provides an implementation in Tcl of the SHA1 message-digest algorithm as specified by
       FIPS PUB 180-1 (1). This algorithm takes a message and generates a 160-bit digest from the input. The
       SHA1  algorithm is related to the MD4 algorithm (2) but has been strengthend against certain types of
       cryptographic attack. SHA1 should be used in preference to MD4 or MD5 in new applications.

       This package also includes support for creating keyed message-digests using the HMAC  algorithm  from
       RFC 2104 (3) with SHA1 as the message-digest.

COMMANDS
       ::sha1::sha1 ?-hex|-bin? [ -channel channel | -file filename | string ]
              The  command  takes  a  message  and  returns the SHA1 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 sha1 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.

       ::sha1::hmac key string

       ::sha1::hmac ?-hex|-bin? -key key [ -channel channel | -file filename | string ]
              Calculate an Hashed Message Authentication digest (HMAC)  using  the  SHA1  digest  algorithm.
              HMACs  are  described  in  RFC  2104  (3)  and provide an SHA1 digest that includes a key. All
              options other than -key are as for the ::sha1::sha1 command.


PROGRAMMING INTERFACE
       For the programmer, the SHA1 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 pro-gramming programming
       gramming interface to the SHA1 hash operates on a token (equivalent to the bucket). You call SHA1Init
       to  obtain  a  token  and  then call SHA1Update as many times as required to add data to the hash. To
       release any resources and obtain the hash value, you then call SHA1Final. An equivalent set of  func-tions functions
       tions 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 if you have the Trf package then this  can  be  used
       otherwise there is a pure-tcl equivalent. The programming interface remains the same in all cases.

       ::sha1::SHA1Init
              Begins a new SHA1 hash. Returns a token ID that must be used for the remaining functions.

       ::sha1::SHA1Update token data
              Add  data  to  the hash identified by token. Calling SHA1Update $token "abcd" is equivalent to
              calling SHA1Update $token "ab" followed by SHA1Update $token "cb". See EXAMPLES.

       ::sha1::SHA1Final token
              Returns the hash value and releases any resources held by this token. Once this  command  com-pletes completes
              pletes  the  token will be invalid. The result is a binary string of 20 bytes representing the
              160 bit SHA1 digest value.

       ::sha1::HMACInit key
              This is equivalent to the ::sha1::SHA1Init command except that it requires the key  that  will
              be included in the HMAC.

       ::sha1::HMACUpdate token data

       ::sha1::HMACFinal token
              These commands are identical to the SHA1 equivalent commands.


EXAMPLES
       % sha1::sha1 "Tcl does SHA1"
       285a6a91c45a9066bf39fcf24425796ef0b2a8bf


       % sha1::hmac Sekret "Tcl does SHA1"
       ae6251fa51b95b18cba2be95eb031d07475ff03c


       % set tok [sha1::SHA1Init]
       ::sha1::1
       % sha1::SHA1Update $tok "Tcl "
       % sha1::SHA1Update $tok "does "
       % sha1::SHA1Update $tok "SHA1"
       % sha1::Hex [sha1::SHA1Final $tok]
       285a6a91c45a9066bf39fcf24425796ef0b2a8bf


REFERENCES
       [1]    "Secure  Hash  Standard",  National  Institute of Standards and Technology, U.S. Department Of
              Commerce, April 1995.  (http://www.itl.nist.gov/fipspubs/fip18_-1.htm)

       [2]    Rivest, R., "The MD4 Message Digest Algorithm", RFC 1320, MIT,  April  1992.  (http://www .rfc-
              editor.org/rfc/rfc132_.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/rfc21_4.txt)


BUGS, IDEAS, FEEDBACK
       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://source -
       forge.net/tracker/? group_id=12883].  Please also report any ideas for enhancements you may  have  for
       either package and/or documentation.

SEE ALSO
       md4, md5, ripemd128, ripemd160

KEYWORDS
       FIPS 180-1, hashing, message-digest, rfc 2104, security, sha1

CATEGORY
       Hashes, checksums, and encryption

COPYRIGHT
       Copyright (c) 2005, Pat Thoyts <patthoyts@users.sourceforge.net>




sha1                                                2.0.3                                            sha1(n)