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aes(n)		      Advanced Encryption Standard (AES)		aes(n)


       aes - Implementation of the AES block cipher

       package require Tcl  8.2

       package require aes  ?1.0.2?

       ::aes::aes ?-mode [ecb|cbc]? ?-dir [encrypt|decrypt]? -key keydata ?-iv
       vector? ?-hex? ?-out channel? ?-chunksize size? [ -in channel | data ]

       ::aes::Init mode keydata iv

       ::aes::Encrypt Key data

       ::aes::Decrypt Key data

       ::aes::Reset Key iv

       ::aes::Final Key


       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

       ::aes::aes ?-mode [ecb|cbc]? ?-dir [encrypt|decrypt]? -key keydata ?-iv
       vector? ?-hex? ?-out channel? ?-chunksize size? [ -in channel | data ]
	      Perform  the  aes	 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 chan‐

	      The -key 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.

	      The -mode and -dir options are optional and default to cbc  mode
	      and  encrypt respectively. The initialization vector -iv takes a
	      16 byte binary argument which defaults to all zeros.  See	 MODES
	      OF OPERATION for more about available modes and their uses.

	      AES  is a 128-bit block cipher. This means that the data must be
	      provided in units that are a multiple of 16 bytes.

       Internal state is maintained in an opaque structure  that  is  returned
       from  the  Init	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 Reset function with a new initialization vector

       ::aes::Init mode keydata iv
	      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
	      MODES OF OPERATION for details about cipher modes.

       ::aes::Encrypt Key data
	      Use  a prepared key acquired by calling Init to encrypt the pro‐
	      vided 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.

       ::aes::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.

       ::aes::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 sched‐
	      ule where the same key data is being used multiple times.

       ::aes::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

       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  encryp‐
	      tion errors will only affect a single block however this is vul‐
	      nerable 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.  This is the default mode of operation for this mod‐

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

       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

       [1]    "Advanced Encryption Standard", Federal  Information  Processing
	      Standards	 Publication  197, 2001 (‐

       Thorsten Schloermann, Pat Thoyts

       This document, and the package it describes, will  undoubtedly  contain
       bugs and other problems.	 Please report such in the category aes of the
       Tcllib  SF  Trackers  [].
       Please  also  report any ideas for enhancements you may have for either
       package and/or documentation.

       blowfish(n), des(n), md5(n), sha1(n)

       aes, block cipher, data integrity, encryption, security

       Hashes, checksums, and encryption

       Copyright (c) 2005, Pat Thoyts <>

aes				     1.0.2				aes(n)

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