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# rc4(n) 1.1.0 tcllib "RC4 Stream Cipher"

## Name

rc4 - Implementation of the RC4 stream cipher

## Synopsis

- package require Tcl 8.2
- package require rc4 ?1.1.0?

- ::rc4::rc4 ?-hex? -key keyvalue ?-command lst? ?-out channel? [ -in channel | -infile filename | string ]
- ::rc4::RC4Init keydata
- ::rc4::RC4 Key data
- ::rc4::RC4Final Key

## Description

This package is an implementation in Tcl of the RC4 stream cipher developed by Ron Rivest of RSA Data Security Inc. The cipher was a trade secret of RSA but was reverse-engineered and published to the internet in 1994. It is used in a number of network protocols for securing communications. To evade trademark restrictions this cipher is sometimes known as ARCFOUR.

## COMMANDS

::rc4::rc4 ?-hex? -key keyvalue ?-command lst? ?-out channel? [ -in channel | -infile filename | string ]

  Perform the RC4 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. Giving the -hex option will return a hexadecimal encoded version of the result if not using an -out channel.

  The data to be processes can be specified either as a string argument to the rc4 command, or as a filename or a pre-opened channel. If the -infile argument is given then the file is opened, the data read and processed and the file is closed. If the -in argument is given then data is read from the channel until the end of file. The channel is not closed. If the -out argument is given then the processing result is written to this channel.

  If -command is provided then the rc4 command does not return anything. Instead the command provided is called with the rc4 result data appended as the final parameter. This is most useful when reading from Tcl channels as a fileevent is setup on the channel and the data processed in chunks

  Only one of -infile, -in or string should be given.

## PROGRAMMING INTERFACE

::rc4::RC4Init keydata

  Initialize a new RC4 key. The keydata is any amount of binary data and is used to initialize the cipher internal state.

::rc4::RC4 Key data

  Encrypt or decrypt the input data using the key obtained by calling RC4Init.

::rc4::RC4Final Key

  This should be called to clean up resources associated with Key. Once this function has been called the key is destroyed.

## EXAMPLES

    % set keydata [binary format H* 0123456789abcdef]
    % rc4::rc4 -hex -key $keydata HelloWorld
    3cf1ae8b7f1c670b612f
    % rc4::rc4 -hex -key $keydata [binary format H* 3cf1ae8b7f1c670b612f]
    HelloWorld

     set Key [rc4::RC4Init "key data"]
     append ciphertext [rc4::RC4 $Key $plaintext]
     append ciphertext [rc4::RC4 $Key $additional_plaintext]
     rc4::RC4Final $Key

     proc ::Finish {myState data} {
         DoStuffWith $myState $data
     }
     rc4::rc4 -in $socket -command [list ::Finish $ApplicationState]

## AUTHORS

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 rc4 of the Tcllib Trackers. 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

aes(n), blowfish(n), des(n)

## Keywords

arcfour, data integrity, encryption, rc4, security, stream cipher

## Category

Hashes, checksums, and encryption

## Copyright

Copyright © 2003, Pat Thoyts <patthoyts@users.sourceforge.net>