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 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
       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 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 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

       ::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://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, 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)
