[SOLVED]Help with matrix "division"(inversion)

[nullschritt]

It has been a couple years since I have worked with matricies, I am writing an encryption algorithm, however I am having a problem with the decryption, I cannot seem to remember exactly how to "divide" matricies, I can't seem to figure out how to properly use the inverse to "undo" the multiplication. maybe someone could give me a hand and show me how please?

here is my code

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func _crypt($text, $key, $binary = 0)
if $binary = 0 Then
$text = StringSplit($text, '')
$number = ''
for $i=1 to $text[0]
$number &= _Base(AscW($text[$i]), $base104)
Next
Else
$number = $Text
EndIf
;compress before encrypt, use binarytostring() chrw() and ascw()
Dim $Original = Binary($number)
Dim $Compressed = _QuickLZ_Compress($Original, 2)
;run through encryption matrix, then compress once more (send in binary safe mode, or use binarytostring).
;convert string to ascw() into a 13xn matrix
$compressed = BinaryToString($Compressed)
$compressed = StringSplit($Compressed, "")
for $i=1 to $Compressed[0]
$Compressed[$i] = AscW($Compressed[$i])
Next
$h = $Compressed[0]/13
$height = round($Compressed[0]/13, 0)
;in order for matrix multiplication to work columns == rows
;so since the keys are 13x13 and we are mutliplying text*key
;the text must have 13 columns 13xN * 13x13 (Columns by Rows [width by heigh])
if $height < $h Then
$height += 1
EndIf
local $ar[$height][13]
$chr = 0
for $i = 0 to $height-1
for $i2= 0 to 12
if $chr < $Compressed[0] Then
$ar[$i][$i2] = $compressed[$Chr]
$Chr += 1
Else
$ar[$i][$i2] = 0
EndIf
next
next
$keys = _loadkey($key)

if $binary = 0 Then
;if not binary choose 15 random keys
local $ran[15]
for $i=0 to 14
$ran[$i] = random(0,12,1)
Next
Else
;else only choose 2
local $ran[2]
for $i=0 to 1
$ran[$i] = random(0,12,1)
Next
EndIf
;record chosen keys

$keysx = "{"&_ArrayToString($ran,';')&"}"
_ArrayDisplay($ar)

$key = _mMul($keys[$ran[0]],$keys[$ran[1]]) ;generate first key from 2 random keys
$enc = _mMul($ar, $key);encrypt text with the key here

if $binary = 0 Then
for $i=1 to 13
$enc = _mMul($enc,$keys[$ran[$i+1]])
;then here we run the encrypted text (with the randomized key) through 13 more levels or random encryption
Next
EndIf
$end = UBound($enc, 1) - 1
$end2 = UBound($enc, 2) -1
$enc[$end][$end2] &= $keysx
;and here we add the numbers of the keys chosen to encrypt the data
$enc = _keytotext($enc, $end, $end2)
;then we convert the matrix to a 1d string representation
;there will also be another level of compression here
Return $enc
EndFunc


Func _decrypt($string, $key)

$keys = _loadkey($key)
$string = _stringtoarray($string)

;will be found in the last element of an array
_ArrayDisplay($string)
local $keysx = StringSplit($string[UBound($string, 1)-1][UBound($string, 2)-1], "{}")
$keysx = StringSplit($keysx[2], ";")
_ArrayDisplay($keysx)

for $i=0 to $keysx[0] - 3
$string = _mMul($string,_inv($keys[$keysx[$keysx[0]-$i]]))
Next
$rankey = _mMul($keys[$keysx[1]],$keys[$keysx[2]])
$string = _mMul($string,_inv($rankey))
_ArrayDisplay($string)

EndFunc

Edited August 18, 2012 by nullschritt

[water]

you can find some matrix functions.

[nullschritt]

you can find some matrix functions.

I know where the matrix functions, you can see they are already in use in my code, I don't understand how to do what I asked with them.

[nullschritt]

Func _decrypt($string, $key)

$keys = _loadkey($key)
$string = _stringtoarray($string)

;will be found in the last element of an array
_ArrayDisplay($string)
local $keysx = StringSplit($string[UBound($string, 1)-1][UBound($string, 2)-1], "{}")
$keysx = StringSplit($keysx[2], ";")
_ArrayDisplay($keysx)
$string[UBound($string, 1)-1][UBound($string, 2)-1] = StringReplace($string[UBound($string, 1)-1][UBound($string, 2)-1], "{"&$keysx[2]&"}", '')
for $i=0 to $keysx[0] - 3
$string = _mMul($string, _inv($keys[$keysx[$keysx[0]-$i]]))
Next
$rankey = _mMul($keys[$keysx[1]],$keys[$keysx[2]])
$string = _mMul($string, _inv($rankey))
_ArrayDisplay($string)

EndFunc

this is my code now, I feel like I am missing something, the resul seems to be close to what it should be, just not near exact.

[nullschritt]

Solved, by reducing the size of the marticies, the numbers used in them, and the number of matricies multiplied(13x13x13x13 to 7x7x7x5), as well as added a function to automatically round the results to whole numbers.

It appears that once the number becomes so large, it becomes impossible to accurately reverse.

Edited August 18, 2012 by nullschritt