Provided by: tcllib_1.21+dfsg-1_all 
NAME
blowfish - Implementation of the Blowfish block cipher
SYNOPSIS
package require Tcl 8.4
package require blowfish ?1.0.5?
::blowfish::blowfish ?-mode [ecb|cbc]? ?-dir [encrypt|decrypt]? -key keydata ?-iv vector?
?-out channel? ?-chunksize size? ?-pad padchar? [ -in channel | ?--? data ]
::blowfish::Init mode keydata iv
::blowfish::Encrypt Key data
::blowfish::Decrypt Key data
::blowfish::Reset Key iv
::blowfish::Final Key
_________________________________________________________________________________________________
DESCRIPTION
This package is an implementation in Tcl of the Blowfish algorithm developed by Bruce
Schneier [1]. Blowfish is a 64-bit block cipher designed to operate quickly on 32 bit
architectures and accepting a variable key length. This implementation supports ECB and
CBC mode blowfish encryption.
COMMANDS
::blowfish::blowfish ?-mode [ecb|cbc]? ?-dir [encrypt|decrypt]? -key keydata ?-iv vector?
?-out channel? ?-chunksize size? ?-pad padchar? [ -in channel | ?--? data ]
Perform the blowfish algorithm on either the data provided by the argument or on
the data read from the -in channel. If an -out channel is given then the result
will be written to this channel.
The -key option must be given. This parameter takes a binary string of variable
length and is used to generate the blowfish key schedule. You should be aware that
creating a key schedule is quite an expensive operation in blowfish so it is worth
reusing the key where possible. See Reset.
The -mode and -dir options are optional and default to cbc mode and encrypt
respectively. The initialization vector -iv takes an 8 byte binary argument which
defaults to 8 zeros. See MODES OF OPERATION for more about available modes and
their uses.
Blowfish is a 64-bit block cipher. This means that the data must be provided in
units that are a multiple of 8 bytes. The blowfish command will by default add nul
characters to pad the input data to a multiple of 8 bytes if necessary. The
programming api commands will never add padding and instead will raise an error if
the input is not a multiple of the block size. The -pad option can be used to
change the padding character or to disable padding if the empty string is provided
as the argument.
PROGRAMMING INTERFACE
::blowfish::Init mode keydata iv
Construct a new blowfish key schedule using the specified key data and the given
initialization vector. The initialization vector is not used with ECB mode but is
important for CBC mode. See MODES OF OPERATION for details about cipher modes.
::blowfish::Encrypt Key data
Use a prepared key acquired by calling Init to encrypt the provided data. The data
argument should be a binary array that is a multiple of the block size of 8 bytes.
The result is a binary array the same size as the input of encrypted data.
::blowfish::Decrypt Key data
Decipher data using the key. Note that the same key may be used to encrypt and
decrypt data provided that the initialization vector is reset appropriately for CBC
mode.
::blowfish::Reset Key iv
Reset the initialization vector. This permits the programmer to re-use a key and
avoid the cost of re-generating the key schedule where the same key data is being
used multiple times.
::blowfish::Final Key
This should be called to clean up resources associated with Key. Once this
function has been called the key may not be used again.
MODES OF OPERATION
Electronic Code Book (ECB)
ECB is the basic mode of all block ciphers. Each block is encrypted independently
and so identical plain text will produce identical output when encrypted with the
same key. Any encryption errors will only affect a single block however this is
vulnerable to known plaintext attacks.
Cipher Block Chaining (CBC)
CBC mode uses the output of the last block encryption to affect the current block.
An initialization vector of the same size as the cipher block size is used to
handle the first block. The initialization vector should be chosen randomly and
transmitted as the first block of the output. Errors in encryption affect the
current block and the next block after which the cipher will correct itself. CBC is
the most commonly used mode in software encryption.
EXAMPLES
% blowfish::blowfish -hex -mode ecb -dir encrypt -key secret01 "hello, world!"
d0d8f27e7a374b9e2dbd9938dd04195a
set Key [blowfish::Init cbc $eight_bytes_key_data $eight_byte_iv]
append ciphertext [blowfish::Encrypt $Key $plaintext]
append ciphertext [blowfish::Encrypt $Key $additional_plaintext]
blowfish::Final $Key
REFERENCES
[1] Schneier, B. "Applied Cryptography, 2nd edition", 1996, ISBN 0-471-11709-9, pub.
John Wiley & Sons.
AUTHORS
Frank Pilhofer, Pat Thoyts
BUGS, IDEAS, FEEDBACK
This document, and the package it describes, will undoubtedly contain bugs and other
problems. Please report such in the category blowfish 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.
When proposing code changes, please provide unified diffs, i.e the output of diff -u.
Note further that attachments are strongly preferred over inlined patches. Attachments can
be made by going to the Edit form of the ticket immediately after its creation, and then
using the left-most button in the secondary navigation bar.
SEE ALSO
3des, des, rc4
KEYWORDS
block cipher, blowfish, cryptography, encryption, security
CATEGORY
Hashes, checksums, and encryption
COPYRIGHT
Copyright (c) 2003, Pat Thoyts <patthoyts@users.sourceforge.net>