1sha256(n) SHA-x Message-Digest Algorithm sha256(n)
2______________________________________________________________________________
6
8 sha256 - SHA256 Message-Digest Algorithm
9
11 package require Tcl 8.2
12 package require sha256 ?1.0.2?
14 ::sha2::sha256 ?-hex|-bin? [ -channel channel | -file filename | string
16 ]
17 ::sha2::sha224 ?-hex|-bin? [ -channel channel | -file filename | string
19 ]
20 ::sha2::hmac key string
22 ::sha2::hmac ?-hex|-bin? -key key [ -channel channel | -file filename |
24 string ]
25 ::sha2::SHA256Init
27 ::sha2::SHA224Init
29 ::sha2::SHA256Update token data
31 ::sha2::SHA256Final token
33 ::sha2::SHA224Final token
35 ::sha2::HMACInit key
37 ::sha2::HMACUpdate token data
39 ::sha2::HMACFinal token
41_________________________________________________________________
43
45 This package provides an implementation in Tcl of the SHA256 and SHA224
46 message-digest algorithms as specified by FIPS PUB 180-1 (1). These
47 algorithms take a message and generates a 256-bit (224-bit) digest from
48 the input. The SHA2 algorithms are related to the SHA1 algorithm.
49 This package also includes support for creating keyed message-digests
51 using the HMAC algorithm from RFC 2104 (3) with SHA256 as the message-
52 digest.
53
55 ::sha2::sha256 ?-hex|-bin? [ -channel channel | -file filename | string
56 ]
57 The command takes a message and returns the SHA256 digest of
58 this message as a hexadecimal string. You may request the result
59 as binary data by giving -bin.
60 The data to be hashed can be specified either as a string argu‐
62 ment to the sha256 command, or as a filename or a pre-opened
63 channel. If the -filename argument is given then the file is
64 opened, the data read and hashed and the file is closed. If the
65 -channel argument is given then data is read from the channel
66 until the end of file. The channel is not closed. NOTE use of
67 the channel or filename options results in the internal use of
68 vwait. To avoid nested event loops in Tk or tclhttpd applica‐
69 tions you should use the incremental programming API (see
70 below).
71 Only one of -file, -channel or string should be given.
73 ::sha2::sha224 ?-hex|-bin? [ -channel channel | -file filename | string
75 ]
76 Like ::sha2::sha256, except that the SHA224 digest is returned.
77 ::sha2::hmac key string
79 ::sha2::hmac ?-hex|-bin? -key key [ -channel channel | -file filename |
81 string ]
82 Calculate an Hashed Message Authentication digest (HMAC) using
83 the SHA256 digest algorithm. HMACs are described in RFC 2104 (3)
84 and provide an SHA256 digest that includes a key. All options
85 other than -key are as for the ::sha2::sha256 command.
86
88 For the programmer, the SHA256 hash can be viewed as a bucket into
89 which one pours data. When you have finished, you extract a value that
90 is derived from the data that was poured into the bucket. The program‐
91 ming interface to the SHA256 hash operates on a token (equivalent to
92 the bucket). You call SHA256Init to obtain a token and then call
93 SHA256Update as many times as required to add data to the hash. To
94 release any resources and obtain the hash value, you then call
95 SHA256Final. An equivalent set of functions gives you a keyed digest
96 (HMAC).
97 If you have critcl and have built the tcllibc package then the imple‐
99 mentation of the hashing function will be performed by compiled code.
100 Failing that there is a pure-tcl equivalent. The programming interface
101 remains the same in all cases.
102 ::sha2::SHA256Init
104 ::sha2::SHA224Init
106 Begins a new SHA256/SHA224 hash. Returns a token ID that must be
107 used for the remaining functions.
108 ::sha2::SHA256Update token data
110 Add data to the hash identified by token. Calling SHA256Update
111 $token "abcd" is equivalent to calling SHA256Update $token "ab"
112 followed by SHA256Update $token "cb". See EXAMPLES. Note that
113 this command is used for both SHA256 and SHA224. Only the ini‐
114 tialization and finalization commands of both hashes differ.
115 ::sha2::SHA256Final token
117 ::sha2::SHA224Final token
119 Returns the hash value and releases any resources held by this
120 token. Once this command completes the token will be invalid.
121 The result is a binary string of 32/28 bytes representing the
122 256/224 bit SHA256 / SHA224 digest value.
123 ::sha2::HMACInit key
125 This is equivalent to the ::sha2::SHA256Init command except that
126 it requires the key that will be included in the HMAC.
127 ::sha2::HMACUpdate token data
129 ::sha2::HMACFinal token
131 These commands are identical to the SHA256 equivalent commands.
132
134 % sha2::sha256 "Tcl does SHA256"
135 0b91043ee484abd83c3e4b08d6034d71b937026379f0f59bda6e625e6e214789
136 % sha2::hmac Sekret "Tcl does SHA256"
139 4f9352c64d655e8a36abe73e6163a9d7a54039877c1c92ec90b07d48d4e854e0
140 % set tok [sha2::SHA256Init]
143 ::sha2::1
144 % sha2::SHA256Update $tok "Tcl "
145 % sha2::SHA256Update $tok "does "
146 % sha2::SHA256Update $tok "SHA256"
147 % sha2::Hex [sha2::SHA256Final $tok]
148 0b91043ee484abd83c3e4b08d6034d71b937026379f0f59bda6e625e6e214789
149
152 [1] "Secure Hash Standard", National Institute of Standards and
153 Technology, U.S. Department Of Commerce, April 1995.
154 (http://www.itl.nist.gov/fipspubs/fip180-1.htm)
155 [2] Rivest, R., "The MD4 Message Digest Algorithm", RFC 1320, MIT,
157 April 1992. (http://www.rfc-editor.org/rfc/rfc1320.txt)
158 [3] Krawczyk, H., Bellare, M. and Canetti, R. "HMAC: Keyed-Hashing
160 for Message Authentication", RFC 2104, February 1997.
161 (http://www.rfc-editor.org/rfc/rfc2104.txt)
162
164 This document, and the package it describes, will undoubtedly contain
165 bugs and other problems. Please report such in the category sha1 of
166 the Tcllib SF Trackers [http://source‐
167 forge.net/tracker/?group_id=12883]. Please also report any ideas for
168 enhancements you may have for either package and/or documentation.
169
171 md4, md5, ripemd128, ripemd160, sha1
172
174 FIPS 180-1, hashing, message-digest, rfc 2104, security, sha256
175
177 Copyright (c) 2008, Andreas Kupries <andreas_kupries@users.sourceforge.net>
178sha1 1.0.2 sha256(n)