shuffling and unshuffling

[iamtheky]

Is there a better way to output and/or read back in, a jumbled mess and its key.  The following is a simple alphabet example of the effect, my major concern is the _arraysearch in the unshuffle and the time penalty I would take on a larger data set.

_ArrayShuffle credit belongs to Malkey I believe

shuffle.au3

expandcollapse popup

Global $bitarray[26] = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"]

Global $aCount[ubound($bitArray)]

For $i = 0 to ubound($bitArray) - 1
$aCount[$i] = $i
Next

_ArrayShuffle($aCount)

$fBits = fileopen("aaa.txt" , 2)
for $i = 0 to ubound($bitArray) - 1
    If $i = ubound($bitArray) - 1 Then
        filewrite($fBits , $bitarray[$aCount[$i]])
    Else
        filewrite($fBits , $bitarray[$aCount[$i]] & "|")
    Endif
Next
fileclose($fBits)

$fKey = fileopen("aaa.key" , 2)
for $i = 0 to ubound($bitArray) - 1
    If $i = ubound($bitArray) - 1 Then
        filewrite($fKey , $acount[$i])
    else
        filewrite($fKey , $acount[$i] & "|")
    Endif
Next
fileclose($fKey)


Func _ArrayShuffle(ByRef $aArray)
    SRandom(@AutoItPID)
    For $i = UBound($aArray) - 1 To 0 Step -1 ; 0-based array
        $j = Random(0, $i, 1)
        $Temp = $aArray[$j]
        $aArray[$j] = $aArray[$i]
        $aArray[$i] = $Temp
    Next
EndFunc   ;==>_ArrayShuffle

unshuffle.au3

#Include <Array.au3>

$sTxt = fileread("aaa.txt")
$aTxt = stringsplit($sTxt , "|" , 2)

$sKey = fileread("aaa.key")
$aKey = stringsplit($sKey , "|" , 2)

Global $unwrap[ubound($aTxt)]

for $i = 0 to ubound($aTxt) - 1
       $match = _ArraySearch($aKey , $i)
       $unwrap[$i] = $aTxt[$match]
   next

_ArrayDisplay($unwrap)

[BrewManNH]

How about this simple solution?

#include <Array.au3>
Global $bitarray[26] = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]

Global $aCount[UBound($bitarray)]
For $i = 0 To UBound($bitarray) - 1
    $aCount[$i] = $i
Next
Global $aCount1 = $aCount
_ArrayDisplay($aCount, "Before")

_ArrayShuffle($aCount)
_ArrayDisplay($aCount, "After Shuffling")
_Unshuffle($aCount)
_ArrayDisplay($aCount, "After Unshuffling")

Func _ArrayShuffle(ByRef $aArray)
    SRandom(@AutoItPID)
    For $i = UBound($aArray) - 1 To 0 Step -1 ; 0-based array
        $j = Random(0, $i, 1)
        $Temp = $aArray[$j]
        $aArray[$j] = $aArray[$i]
        $aArray[$i] = $Temp
    Next
EndFunc   ;==>_ArrayShuffle

Func _Unshuffle(ByRef $aIn)
    $aIn = $aCount1
EndFunc   ;==>_Unshuffle

The _Unshuffle function is just _ArraySwap with a new name.

[iamtheky]

unshuffle's inputs only being the keyfile and the shuffled text file.  All in the same script I would just show the $bitArray again

[Gianni]

hi boththose

I think in "unshuffle.au3" _ArraySearch ($ aKey, $ i) it is not necessary

you can simply and quickly decode in this way:

for $i = 0 to ubound($aTxt) - 1

       ; $match = _ArraySearch($aKey , $i)
       ; $unwrap[$i] = $aTxt[$match]

       $unwrap[$aKey[$i]] = $aTxt[$i]

next

[iamtheky]

That is too easy, many thanks for the help!  Now onto *conditions and masking large data sets with obscure keys.

Edited July 16, 2013 by boththose

[Gianni]

That is too easy, many thanks for the help!  Now onto *conditions and masking large data sets with obscure keys.

 

[iamtheky]

All part of a much larger steganography effort.  I can set hidden data, I can now jumble that data. I figure set enough bogus elements in the key file, likewise some bogus elements in the data and the result would be a pretty healthy attempt at hiding in plain sight.

[BrewManNH]

Probably would have helped immensely if you had explained the purpose of the script(s) rather than asking if there was a better way to unshuffle the array. Not to mention, a simple substitution cipher could probably be broken in a matter of seconds with enough text to work with.