John Davidson

Message:

Ok so i've been learning a couple of weeks about encryption, a friend of mine have an encryption function in VB.Net and he gave it to me so i can transfered it to PHP for some test.

the decryptions works 50% of the times.
Sometimes i get an accurate result and the other i just get some encrypted stuff.
I dont know where i am wrong, i've been playing with these codes the last 2 weeks and i getting me mad.

VB.NET Code

#Region "Llaves"

Private patron_busqueda As String = "3AnB12CDEopFIJKÑcdOP0QRSTU56VWXYZabe9fLMNghi7jklmñqrstuvwx4yz8GH"

Private Patron_encripta As String = "B0CDdE3GHIst8JKL6MNPQR2STUVWX7YZabcÑ5OefghijklFmnñ4opqruv1wxyz9A"

#End Region

Public Function DesEncriptarCadena(ByVal cadena As String) As String

    Dim idx As Integer

    Dim result As String = ""



    For idx = 0 To cadena.Length - 1

        result += DesEncriptarCaracter(cadena.Substring(idx, 1), cadena.Length, idx)

    Next

    Return result

End Function

Private Function DesEncriptarCaracter(ByVal caracter As String, _

                 ByVal variable As Integer, ByVal a_indice As Integer) As String

    Dim indice As Integer



    If Patron_encripta.IndexOf(caracter) <> -1 Then

        If (Patron_encripta.IndexOf(caracter) - variable - a_indice) > 0 Then

            indice = (Patron_encripta.IndexOf(caracter) - variable - a_indice) Mod Patron_encripta.Length

        Else

            'La línea está cortada por falta de espacio

            indice = (patron_busqueda.Length) + ((Patron_encripta.IndexOf(caracter) - variable - a_indice) Mod Patron_encripta.Length)

        End If

        indice = indice Mod Patron_encripta.Length

        Return patron_busqueda.Substring(indice, 1)

    Else

        Return caracter

    End If

End Function

PHP Code

$patron_busqueda = "3AnB12CDEopFIJKNcdOP0QRSTU56VWXYZabe9fLMNghi7jklmnqrstuvwx4yz8GH";

$pb=str_split($patron_busqueda,1);

$pblargo=strlen($patron_busqueda);

$patron_encripta = "B0CDdE3GHIst8JKL6MNPQR2STUVWX7YZabcN5OefghijklFmnn4opqruv1wxyz9A";

$pe=str_split($patron_encripta,1);

$pelargo=strlen($patron_encripta);

$i=0;

$encrypted=str_split($res,1);

$decrypted="";

$res="5555444433332222"

  $largo=strlen($res);

while ( $i < $largo) {

    $x = array_search($encrypted[$i], $pe);

    $x = $x-$largo-$i;

   if ($x>=0) {

            $z = $pb[$x];

            $decrypted=$decrypted.$z;

            $i=$i+1;

    }else{

    $x = $pblargo+($x);

    $z = $pb[$x];

    $decrypted=$decrypted.$z;

    $i=$i+1;

    }

 }

Any guide/help would be much appreciated

---

My Answer:
It looks like there are a few issues in your PHP code that may be causing the decryption to not work correctly. Here are some suggestions to help you troubleshoot and fix the issue:

1. Check the variable names: Make sure that the variable names in your PHP code match the ones in the VB.Net code. For example, in your PHP code, you are using $res before it is defined. Make sure to define $res before using it.

2. Check the logic in the decryption function: Double-check the logic in your decryption function to ensure that it matches the logic in the VB.Net code. Pay close attention to the calculations and conditions used to decrypt each character.

3. Debugging: Add some debugging statements to your PHP code to print out the values of variables at different points in the decryption process. This can help you identify where the decryption is going wrong.

4. Test with different inputs: Try decrypting different encrypted strings to see if the issue is specific to a certain input. This can help you narrow down the problem.

5. Compare outputs: Compare the output of your PHP decryption function with the output of the VB.Net decryption function for the same input. This can help you identify any discrepancies in the results.

By following these suggestions and carefully comparing your PHP code with the VB.Net code, you should be able to identify and fix the issues causing the decryption to not work correctly.