'\"
'\" Generated from file 'aes\&.man' by tcllib/doctools with format 'nroff'
'\" Copyright (c) 2005, Pat Thoyts <patthoyts@users\&.sourceforge\&.net>
'\" Copyright (c) 2012-2014, Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>
'\"
.TH "aes" n 1\&.2\&.1 tcllib "Advanced Encryption Standard (AES)"
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.SH NAME
aes \- Implementation of the AES block cipher
.SH SYNOPSIS
package require \fBTcl  8\&.5\fR
.sp
package require \fBaes  ?1\&.2\&.1?\fR
.sp
\fB::aes::aes\fR ?\fI-mode [ecb|cbc]\fR? ?\fI-dir [encrypt|decrypt]\fR? \fI-key keydata\fR ?\fI-iv vector\fR? ?\fI-hex\fR? ?\fI-out channel\fR? ?\fI-chunksize size\fR? [ \fI-in channel\fR | ?\fB--\fR? \fIdata\fR ]
.sp
\fB::aes::Init\fR \fImode\fR \fIkeydata\fR \fIiv\fR
.sp
\fB::aes::Encrypt\fR \fIKey\fR \fIdata\fR
.sp
\fB::aes::Decrypt\fR \fIKey\fR \fIdata\fR
.sp
\fB::aes::Reset\fR \fIKey\fR \fIiv\fR
.sp
\fB::aes::Final\fR \fIKey\fR
.sp
.BE
.SH DESCRIPTION
.PP
This is an implementation in Tcl of the Advanced Encryption Standard
(AES) as published by the U\&.S\&. National Institute of Standards and
Technology [1]\&. AES is a 128-bit block cipher with a variable
key size of 128, 192 or 256 bits\&. This implementation supports ECB and
CBC modes\&.
.SH COMMANDS
.TP
\fB::aes::aes\fR ?\fI-mode [ecb|cbc]\fR? ?\fI-dir [encrypt|decrypt]\fR? \fI-key keydata\fR ?\fI-iv vector\fR? ?\fI-hex\fR? ?\fI-out channel\fR? ?\fI-chunksize size\fR? [ \fI-in channel\fR | ?\fB--\fR? \fIdata\fR ]
Perform the \fBaes\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 either 16, 24 or 32 bytes in length and is used to generate the
key schedule\&.
.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 a 16 byte binary argument which defaults to all zeros\&.
See \fBMODES OF OPERATION\fR for more about available modes and
their uses\&.
.sp
AES is a 128-bit block cipher\&. This means that the data must be
provided in units that are a multiple of 16 bytes\&.
.PP
.SH "PROGRAMMING INTERFACE"
Internal state is maintained in an opaque structure that is returned
from the \fBInit\fR function\&. In ECB mode the state is not affected by
the input but for CBC mode some input dependent state is maintained
and may be reset by calling the \fBReset\fR function with a new
initialization vector value\&.
.TP
\fB::aes::Init\fR \fImode\fR \fIkeydata\fR \fIiv\fR
Construct a new AES 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::aes::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 AES block size of 16 bytes\&. The result is a binary
array the same size as the input of encrypted data\&.
.TP
\fB::aes::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::aes::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::aes::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\&. This is the default mode
of operation for this module\&.
.PP
.SH EXAMPLES
.CS


% set nil_block [string repeat \\\\0 16]
% aes::aes -hex -mode cbc -dir encrypt -key $nil_block $nil_block
66e94bd4ef8a2c3b884cfa59ca342b2e

.CE
.CS


set Key [aes::Init cbc $sixteen_bytes_key_data $sixteen_byte_iv]
append ciphertext [aes::Encrypt $Key $plaintext]
append ciphertext [aes::Encrypt $Key $additional_plaintext]
aes::Final $Key

.CE
.SH REFERENCES
.IP [1]
"Advanced Encryption Standard",
Federal Information Processing Standards Publication 197, 2001
(\fIhttp://csrc\&.nist\&.gov/publications/fips/fips197/fips-197\&.pdf\fR)
.PP
.SH AUTHORS
Thorsten Schloermann, 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 \fIaes\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\&.
.PP
When proposing code changes, please provide \fIunified diffs\fR,
i\&.e the output of \fBdiff -u\fR\&.
.PP
Note further that \fIattachments\fR are strongly preferred over
inlined patches\&. Attachments can be made by going to the \fBEdit\fR
form of the ticket immediately after its creation, and then using the
left-most button in the secondary navigation bar\&.
.SH "SEE ALSO"
blowfish(n), des(n), md5(n), sha1(n)
.SH KEYWORDS
aes, block cipher, data integrity, encryption, security
.SH CATEGORY
Hashes, checksums, and encryption
.SH COPYRIGHT
.nf
Copyright (c) 2005, Pat Thoyts <patthoyts@users\&.sourceforge\&.net>
Copyright (c) 2012-2014, Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>

.fi