'\"
'\" Generated from file 'blowfish\&.man' by tcllib/doctools with format 'nroff'
'\" Copyright (c) 2003, Pat Thoyts <patthoyts@users\&.sourceforge\&.net>
'\"
.TH "blowfish" n 1\&.0\&.3 tcllib "Blowfish Block Cipher"
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.SH NAME
blowfish \- Implementation of the Blowfish block cipher
.SH SYNOPSIS
package require \fBTcl  8\&.4\fR
.sp
package require \fBblowfish  ?1\&.0\&.4?\fR
.sp
\fB::blowfish::blowfish\fR ?\fI-mode [ecb|cbc]\fR? ?\fI-dir [encrypt|decrypt]\fR? \fI-key keydata\fR ?\fI-iv vector\fR? ?\fI-out channel\fR? ?\fI-chunksize size\fR? ?\fI-pad padchar\fR? [ \fI-in channel\fR | ?\fI--\fR? \fIdata\fR ]
.sp
\fB::blowfish::Init\fR \fImode\fR \fIkeydata\fR \fIiv\fR
.sp
\fB::blowfish::Encrypt\fR \fIKey\fR \fIdata\fR
.sp
\fB::blowfish::Decrypt\fR \fIKey\fR \fIdata\fR
.sp
\fB::blowfish::Reset\fR \fIKey\fR \fIiv\fR
.sp
\fB::blowfish::Final\fR \fIKey\fR
.sp
.BE
.SH DESCRIPTION
.PP
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\&.
.SH COMMANDS
.TP
\fB::blowfish::blowfish\fR ?\fI-mode [ecb|cbc]\fR? ?\fI-dir [encrypt|decrypt]\fR? \fI-key keydata\fR ?\fI-iv vector\fR? ?\fI-out channel\fR? ?\fI-chunksize size\fR? ?\fI-pad padchar\fR? [ \fI-in channel\fR | ?\fI--\fR? \fIdata\fR ]
Perform the \fBblowfish\fR algorithm on either the data provided
by the argument or on the data read from the \fI-in\fR channel\&. If
an \fI-out\fR channel is given then the result will be written to
this channel\&.
.sp
The \fI-key\fR option must be given\&. This parameter takes a binary
string of variable length and is used to generate the \fBblowfish\fR
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 \fBReset\fR\&.
.sp
The \fI-mode\fR and \fI-dir\fR options are optional and default to cbc
mode and encrypt respectively\&. The initialization vector \fI-iv\fR
takes an 8 byte binary argument which defaults to 8 zeros\&.
See \fBMODES OF OPERATION\fR for more about available modes and
their uses\&.
.sp
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 \fBblowfish\fR
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 \fI-pad\fR option can be used to
change the padding character or to disable padding if the empty string
is provided as the argument\&.
.PP
.SH "PROGRAMMING INTERFACE"
.TP
\fB::blowfish::Init\fR \fImode\fR \fIkeydata\fR \fIiv\fR
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 \fBMODES OF OPERATION\fR for details about cipher modes\&.
.TP
\fB::blowfish::Encrypt\fR \fIKey\fR \fIdata\fR
Use a prepared key acquired by calling \fBInit\fR 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\&.
.TP
\fB::blowfish::Decrypt\fR \fIKey\fR \fIdata\fR
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\&.
.TP
\fB::blowfish::Reset\fR \fIKey\fR \fIiv\fR
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\&.
.TP
\fB::blowfish::Final\fR \fIKey\fR
This should be called to clean up resources associated with \fIKey\fR\&.
Once this function has been called the key may not be used again\&.
.PP
.SH "MODES OF OPERATION"
.TP
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\&.
.TP
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\&.
.PP
.SH EXAMPLES
.CS


% blowfish::blowfish -hex -mode ecb -dir encrypt -key secret01 "hello, world!"
d0d8f27e7a374b9e2dbd9938dd04195a

.CE
.CS


 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

.CE
.SH REFERENCES
.IP [1]
Schneier, B\&. "Applied Cryptography, 2nd edition", 1996,
ISBN 0-471-11709-9, pub\&. John Wiley & Sons\&.
.PP
.SH AUTHORS
Frank Pilhofer, Pat Thoyts
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems\&.
Please report such in the category \fIblowfish\fR of the
\fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&.
Please also report any ideas for enhancements you may have for either
package and/or documentation\&.
.SH "SEE ALSO"
3des, des, rc4
.SH KEYWORDS
block cipher, blowfish, cryptography, encryption, security
.SH CATEGORY
Hashes, checksums, and encryption
.SH COPYRIGHT
.nf
Copyright (c) 2003, Pat Thoyts <patthoyts@users\&.sourceforge\&.net>

.fi