Converting a Visual Basic function to PHP - php

Question

I have a Visual Basic function and I am not that familiar with VB. I need to convert it to PHP and have made a start. There are a couple of functions I'm not sure how to replicate and am looking for some help with this and to see if I have got the nesting right etc. In the following code, there is the vb function and then my attempt at te php version. it is not complete and in the php version I have commented out the vb parts I am not sure about. Can anyone help put me on the right lines?
Public Function gfnCrypt(ByVal Expression As String, ByVal Password As String) As String
'RC4 Encryption
Dim rb(0 To 255) As Integer, X As Long, Y As Long, Z As Long, Key() As Byte, ByteArray() As Byte, temp As Byte
On Error Resume Next
If Len(Password) = 0 Then
Exit Function
End If
If Len(Expression) = 0 Then
Exit Function
End If
If Len(Password) > 256 Then
Key() = StrConv(Left$(Password, 256), vbFromUnicode)
Else
Key() = StrConv(Password, vbFromUnicode)
End If
For X = 0 To 255
rb(X) = X
Next X
X = 0
Y = 0
Z = 0
For X = 0 To 255
Y = (Y + rb(X) + Key(X Mod Len(Password))) Mod 256
temp = rb(X)
rb(X) = rb(Y)
rb(Y) = temp
Next X
X = 0
Y = 0
Z = 0
ByteArray() = StrConv(Expression, vbFromUnicode)
For X = 0 To Len(Expression)
Y = (Y + 1) Mod 256
Z = (Z + rb(Y)) Mod 256
temp = rb(Y)
rb(Y) = rb(Z)
rb(Z) = temp
ByteArray(X) = ByteArray(X) Xor (rb((rb(Y) + rb(Z)) Mod 256))
Next X
gfnCrypt = StrConv(ByteArray, vbUnicode)
End Function
And in PHP:
function gfnCrypt($mywebpassword, $mywebkey) {
//'RC4 Encryption
//Dim rb(0 To 255) As Integer, X As Long, Y As Long, Z As Long, Key() As Byte, ByteArray() As Byte, temp As Byte
if(strlen($mywebpassword) == 0){
return false;
}
if(strlen($mywebkey) == 0){
return false;
}
if(strlen($mywebpassword) > 256){
//Key() = StrConv(Left$(Password, 256), vbFromUnicode)
}else{
//Key() = StrConv(Password, vbFromUnicode)
}
$rb=array();
for($x=0;$x=255;$x++){
$rb['x'] = $x;
for($x=0;$x=255;$x++){
$y = ($y + $rb['x'];// + Key(X Mod Len(Password))) Mod 256
$temp = $rb['x'];
$rb['x'] = $rb[$y];
$rb[$y] = $temp;
//ByteArray() = StrConv(Expression, vbFromUnicode)
for($x=0;$x=strlen($mywebpassword), $x++){
$y = ($y + 1);// Mod 256
$z = ($z + $rb[$y]);// Mod 256
$temp = $rb[$y];
$rb[$y] = $rb[$z];
$rb[$z] = $temp;
//ByteArray(X) = ByteArray(X) Xor (rb((rb(Y) + rb(Z)) Mod 256))
}
}
}
//gfnCrypt = StrConv(ByteArray, vbUnicode)
return $gfnCrypt;
}

Answer 1

The arithmetic modulo can be used in php using % operator.
$modulus = $a % $b
I think you will get errors with your 3 embedded for (x…) loops by the way.
To access an element of the array (the $ith for instance) don't use $array['i'] but $array[$i].
The StrConv must be a ut8_encode and the left stuff can be done with substr($string, 0, 255).
References: utf8_encode substr

Answer 2

If you are trying to do RC4 encryption in PHP then you may wan't to take a look at the project at this link http://code.google.com/p/rc4crypt/

Answer 3

I really hope you have some unit tests to test that:
function gfnCrypt($mywebpassword, $mywebkey) {
//'RC4 Encryption
//Dim rb(0 To 255) As Integer, X As Long, Y As Long, Z As Long, Key() As Byte, ByteArray() As Byte, temp As Byte
rb = array();
Key = array();
ByteArray = array();
if(strlen($mywebpassword) == 0){
return false;
}
if(strlen($mywebkey) == 0){
return false;
}
if(strlen($mywebpassword) > 256){
//Key() = StrConv(Left$(Password, 256), vbFromUnicode)
Key[] = ut8_encodesubstr(Password, 0, 256));
}else{
//Key() = StrConv(Password, vbFromUnicode)
Key[] = ut8_encode(Password);
}
$rb=array();
for($x=0;$x=255;$x++){
$rb['x'] = $x;
for($x=0;$x=255;$x++){
$y = ($y + $rb['x'] + Key(X % strlen(Password))) % 256;
$temp = $rb['x'];
$rb['x'] = $rb[$y];
$rb[$y] = $temp;
//ByteArray() = StrConv(Expression, vbFromUnicode)
ByteArray[] = ut8_encode(Expression);
for($x=0;$x=strlen($mywebpassword), $x++){
$y = ($y + 1);// Mod 256
$z = ($z + $rb[$y]);// Mod 256
$temp = $rb[$y];
$rb[$y] = $rb[$z];
$rb[$z] = $temp;
//ByteArray(X) = ByteArray(X) Xor (rb((rb(Y) + rb(Z)) Mod 256))
ByteArray[X] = (ByteArray[X] ^= (rb[(rb[Y] + rb[Z]] % 256)]);
}
}
}
//gfnCrypt = StrConv(ByteArray, vbUnicode)
gfnCrypt = ut8_encode(ByteArray);
return $gfnCrypt;
}
I finished the code you started, but it seems really wrong (for example, why nest 3 for loops, using the same variable ?). It doesn't even seem to match the initial VB code...