


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 argu-
              ment to the sha1 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



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


              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  programming
       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 equiv-
       alent set of functions gives you a keyed digest (HMAC).

       If  you  have critcl and have built the tcllibc package then the imple-
       mentation of the hashing function will be performed by  compiled  code.
       Failing  that  if you have the Trf package then this can be used other-
       wise 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 completes 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




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


       ::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/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)


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>




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