Skip to content

Instantly share code, notes, and snippets.

@HarmJ0y HarmJ0y/RC4.ps1
Last active Sep 16, 2019

Embed
What would you like to do?
PowerShell RC4 Implementation
function ConvertTo-Rc4ByteStream {
<#
.SYNOPSIS
Converts an input byte array to a RC4 cipher stream using the specified key.
Author: @harmj0y
License: BSD 3-Clause
Required Dependencies: None
Optional Dependencies: None
.PARAMETER InputObject
The input byte array to encrypt with the RC4 cipher.
.PARAMETER Key
The byte array of the RC4 key to use.
.EXAMPLE
$Enc = [System.Text.Encoding]::ASCII
$Data = $Enc.GetBytes('This is a test! This is only a test.')
$Key = $Enc.GetBytes('SECRET')
($Data | ConvertTo-Rc4ByteStream -Key $Key | ForEach-Object { "{0:X2}" -f $_ }) -join ' '
.LINK
https://en.wikipedia.org/wiki/RC4
http://www.remkoweijnen.nl/blog/2013/04/05/rc4-encryption-in-powershell/
#>
[CmdletBinding()]
Param (
[Parameter(Position = 0, Mandatory = $True, ValueFromPipeline = $True)]
[ValidateNotNullOrEmpty()]
[Byte[]]
$InputObject,
[Parameter(Position = 1, Mandatory = $True)]
[ValidateNotNullOrEmpty()]
[Byte[]]
$Key
)
begin {
# key-scheduling algorithm
[Byte[]] $S = 0..255
$J = 0
0..255 | ForEach-Object {
$J = ($J + $S[$_] + $Key[$_ % $Key.Length]) % 256
$S[$_], $S[$J] = $S[$J], $S[$_]
}
$I = $J = 0
}
process {
# pseudo-random generation algorithm (PRGA) combined with XOR logic
ForEach($Byte in $InputObject) {
$I = ($I + 1) % 256
$J = ($J + $S[$I]) % 256
$S[$I], $S[$J] = $S[$J], $S[$I]
$Byte -bxor $S[($S[$I] + $S[$J]) % 256]
}
}
}
# minimized RC4 function
$R={$D,$K=$Args;$S=0..255;0..255|%{$J=($J+$S[$_]+$K[$_%$K.Length])%256;$S[$_],$S[$J]=$S[$J],$S[$_]};$D|%{$I=($I+1)%256;$H=($H+$S[$I])%256;$S[$I],$S[$H]=$S[$H],$S[$I];$_-bxor$S[($S[$I]+$S[$H])%256]}}
$Enc = [System.Text.Encoding]::ASCII
$UEnc = [System.Text.Encoding]::UNICODE
$Data = $Enc.GetBytes('This is a test! This is only a test.')
$Key = $Enc.GetBytes('SecretPassword')
($Data | ConvertTo-Rc4ByteStream -Key $Key | ForEach-Object { "{0:X2}" -f $_ }) -join ' '
(& $R $data $key | ForEach-Object { "{0:X2}" -f $_ }) -join ' '
$Enc = [System.Text.Encoding]::ASCII
$D = $Enc.GetBytes('This is a test! This is only a test.')
$K = $Enc.GetBytes('SecretPassword')
# *almost* in a single tweet
-join[Char[]]([Text.Encoding]::Unicode|% *es '匤〽⸮㔲㬵⠤匤簩笥䨤⠽䨤␫孓弤⭝䬤⑛╟䬤䌮畯瑮⥝㈥㘵␻孓弤ⱝ匤⑛嵊␽孓䨤ⱝ匤⑛嵟㭽䐤╼⑻㵉⬫䤤㈥㘵␻㵈␨⭈匤⑛嵉┩㔲㬶匤⑛嵉␬孓䠤㵝匤⑛嵈␬孓䤤㭝弤戭潸⑲孓␨孓䤤⭝匤⑛嵈┩㔲崶⁽')|IEX
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.