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.
If the string to hash can be mistaken for an option (leading dash
"-"), use the option -- before it to terminate option
processing and force interpretation as a string.
- ::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.
If the string to hash can be mistaken for an option (leading dash
"-"), use the option -- before it to terminate option
processing and force interpretation as a string.
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 Trackers [
http://core.tcl.tk/tcllib/reportlist]. 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>