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

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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

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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  incre-
	      mental 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

COPYRIGHT

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

sha1								       2.0.3								   sha1(n)