Encrypt in PHP not working as expected...

Question

Hi,

I have a very silly situation, i am receiving an encrypted string from VB.NET in PHP. I am able to decrypt the key. But when i want to encrypt the result and get the encrtypted string i get a mismatch. Can anyone help me out please....

Below is the PHP CODE.

<?php

//$syscode=$_REQUEST['syscode'];
//The actual string is "blueberry" which is encrypted in VB.NET and sent to PHP
$syscode = "8yN73RDmMFuXo9ux8QKC6w=="; //This is the encrypted string as received from VB.NET
echo "Original Encrypted String Received from VB.NET: <br>".$syscode;
echo "<br><br>";
Decrypt($syscode);
echo "<br><br>";
Encrypt("blueberry");


function Decrypt($strToDecrypt){
global $strD;
$key64 = "cPSQAC05GBXzMhRRz7tm8cqg+vHdHyN5";
$iv64 = "jIShBJVBfXo=";
$encryptedString64 = $strToDecrypt;
$keybytes = base64_decode($key64);
$ivbytes = base64_decode($iv64);

$encryptedStringbytes = base64_decode($encryptedString64);

// use mcrypt library for encryption
$decryptRaw = mcrypt_decrypt(MCRYPT_3DES, $keybytes, $encryptedStringbytes, MCRYPT_MODE_CBC, $ivbytes);
$decryptString=trim($decryptRaw,"\x00..\x1F");
print "Decrypted by PHP:<br>$decryptString<br/>"; //The decrypted string should be "blueberry"
}

function Encrypt($strToEncrypt){
$key64 = "cPSQAC05GBXzMhRRz7tm8cqg+vHdHyN5";
$iv64 = "jIShBJVBfXo=";
$keybytes = base64_decode($key64);
$ivbytes = base64_decode($iv64);

// use mcrypt library for encryption
$encryptRaw = mcrypt_encrypt(MCRYPT_3DES, $keybytes, $strToEncrypt, MCRYPT_MODE_CBC, $ivbytes);
$encryptString=trim($encryptRaw,"\x00..\x1F");
$encryptString=(base64_encode(trim($encryptRaw)));

print "Encrypted in PHP:<br>$encryptString<br/>"; //This where the PHP encrypted result is not matching the VB.NET encryption result.
}
?>

Answer 1

Are you using the same iv for VB as well as PHP encryption? Also, try removing the trim after encryption - it is not needed. You need trim only after decryption.

Answer 2

The VB.NET code i am using on the appliation side is below...

Imports System
Imports System.Text
Imports System.Security.Cryptography
Imports System.IO

Module Crypto
    Public Function Decrypt(ByVal strToDecrypt As String) As String
        Try

            'initialize our key
            Dim tripleDESKey As SymmetricAlgorithm = SymmetricAlgorithm.Create("TripleDES")
            tripleDESKey.Key = Convert.FromBase64String("cPSQAC05GBXzMhRRz7tm8cqg+vHdHyN5")
            tripleDESKey.IV = Convert.FromBase64String("jIShBJVBfXo=")

            'load our encrypted value into a memory stream
            Dim encryptedValue As String = strToDecrypt
            Dim encryptedStream As MemoryStream = New MemoryStream()
            encryptedStream.Write(Convert.FromBase64String(encryptedValue), 0, Convert.FromBase64String(encryptedValue).Length)
            encryptedStream.Position = 0

            'set up a stream to do the decryption
            Dim cs As CryptoStream = New CryptoStream(encryptedStream, tripleDESKey.CreateDecryptor, CryptoStreamMode.Read)
            Dim decryptedStream As MemoryStream = New MemoryStream()
            Dim buf() As Byte = New Byte(2048) {}
            Dim bytesRead As Integer

            'keep reading from encrypted stream via the crypto stream
            'and store that in the decrypted stream
            bytesRead = cs.Read(buf, 0, buf.Length)
            While (bytesRead > 0)
                decryptedStream.Write(buf, 0, bytesRead)
                bytesRead = cs.Read(buf, 0, buf.Length)
            End While

            'reassemble the decrypted stream into a string    
            Dim decryptedValue As String = Encoding.ASCII.GetString(decryptedStream.ToArray())


            Return (decryptedValue.ToString())

        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Function

    Public Function Encrypt(ByVal strToEncrypt As String) As String
        Dim sa As SymmetricAlgorithm = SymmetricAlgorithm.Create("TripleDES")
        sa.Key = Convert.FromBase64String("cPSQAC05GBXzMhRRz7tm8cqg+vHdHyN5")
        sa.IV = Convert.FromBase64String("jIShBJVBfXo=")

        Dim inputByteArray() As Byte = Encoding.ASCII.GetBytes(strToEncrypt)
        Dim mS As MemoryStream = New MemoryStream()

        Dim trans As ICryptoTransform = sa.CreateEncryptor
        Dim buf() As Byte = New Byte(2048) {}
        Dim cs As CryptoStream = New CryptoStream(mS, trans, CryptoStreamMode.Write)
        cs.Write(inputByteArray, 0, inputByteArray.Length)
        cs.FlushFinalBlock()

        Return Convert.ToBase64String(mS.ToArray).ToString
    End Function
End Module