[comment {-*- tcl -*- doctools manpage}]
[vset VERSION 1.2.0]
[manpage_begin rc4 n [vset VERSION]]
[see_also aes(n)]
[see_also blowfish(n)]
[see_also des(n)]
[keywords arcfour]
[keywords {data integrity}]
[keywords encryption]
[keywords rc4]
[keywords security]
[keywords {stream cipher}]
[copyright {2003, Pat Thoyts <patthoyts@users.sourceforge.net>}]
[moddesc   {RC4 Stream Cipher}]
[titledesc {Implementation of the RC4 stream cipher}]
[category  {Hashes, checksums, and encryption}]
[require Tcl "8.5 9"]
[require rc4 [opt [vset VERSION]]]
[description]
[para]

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.

[section {COMMANDS}]

[list_begin definitions]

[call [cmd "::rc4::rc4"] \
     [opt "[arg -hex]"] \
     [arg "-key keyvalue" ] \
     [opt [arg "-command lst"]] \
     [opt [arg "-out channel"]] \
     [lb] [arg "-in channel"] | \
     [arg "-infile filename"] | [arg "string"] [rb]]

Perform the RC4 algorithm on either the data provided by the argument
or on the data read from the [arg "-in"] channel. If an [arg "-out"]
channel is given then the result will be written to this channel.
Giving the [arg "-hex"] option will return a hexadecimal encoded
version of the result if not using an [arg -out] channel.

[para]

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
[arg "-infile"] argument is given then the file is opened, the data read
and processed and the file is closed. If the [arg "-in"] argument is
given then data is read from the channel until the end of file. The
channel is not closed. If the [arg "-out"] argument is given then the
processing result is written to this channel.

[para]

If [arg "-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

[para]

Only one of [arg "-infile"], [arg "-in"] or [arg "string"] should be given.

[list_end]

[section "PROGRAMMING INTERFACE"]

[list_begin definitions]

[call [cmd "::rc4::RC4Init"] [arg "keydata"]]

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

[call [cmd "::rc4::RC4"] [arg "Key"] [arg "data"]]

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

[call [cmd "::rc4::RC4Final"] [arg "Key"]]

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

[list_end]

[section "EXAMPLES"]

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

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

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

[section "AUTHORS"]
Pat Thoyts

[vset CATEGORY rc4]
[include ../common-text/feedback.inc]
[manpage_end]
