John Davidson

Message:

when I try to encrypt using openssl_encrypt PHP I get square spaces at the end decrypted data which is shown in attached image

My API response is getting failure due to getting extra characters during decryption done by .NET side..

How can i resolve this issue please help

C#

public static string Decrypt(String encryptedText, String VendorKey, String Token)

{

    var encryptedBytes = Convert.FromBase64String(encryptedText);

    return Encoding.UTF8.GetString(Decrypt(encryptedBytes, GetRijndaelManaged(VendorKey,Token)));

}



private static byte[] Decrypt(byte[] encryptedData, RijndaelManaged rijndaelManaged)

{

    return rijndaelManaged.CreateDecryptor()

                .TransformFinalBlock(encryptedData, 0, encryptedData.Length);

}



public static RijndaelManaged GetRijndaelManaged(String VendorKey, String Token)

{

    var keyBytes = new byte[32];

    var ivBytes = new byte[16];

            

    var secretKeyBytes = Encoding.UTF8.GetBytes(VendorKey + Token);

    Array.Copy(secretKeyBytes, keyBytes, Math.Min(keyBytes.Length, secretKeyBytes.Length));



    var ivKeyBytes = Encoding.UTF8.GetBytes(VendorKey);

    Array.Copy(ivKeyBytes, ivBytes, Math.Min(ivBytes.Length, ivKeyBytes.Length));



    return new RijndaelManaged

    {

       Mode = CipherMode.CBC,

       Padding = PaddingMode.Zeros,

       KeySize = 256, 

       BlockSize = 128, 

       Key = keyBytes,

       IV = ivKeyBytes

    };

}



public static string Encrypt(String plainText, String VendorKey, String Token)

{

    var plainBytes = Encoding.UTF8.GetBytes(plainText);

    return Convert.ToBase64String(Encrypt(plainBytes, GetRijndaelManaged(VendorKey, Token)));

}



private static byte[] Encrypt(byte[] plainBytes, RijndaelManaged rijndaelManaged)

{

    return rijndaelManaged.CreateEncryptor()

                .TransformFinalBlock(plainBytes, 0, plainBytes.Length);

}



public static RijndaelManaged GetRijndaelManaged(String VendorKey, String Token)

{

    var keyBytes = new byte[32];

    var ivBytes = new byte[16];

            

    var secretKeyBytes = Encoding.UTF8.GetBytes(VendorKey + Token);

    Array.Copy(secretKeyBytes, keyBytes, Math.Min(keyBytes.Length, secretKeyBytes.Length));



    var ivKeyBytes = Encoding.UTF8.GetBytes(VendorKey);

    Array.Copy(ivKeyBytes, ivBytes, Math.Min(ivBytes.Length, ivKeyBytes.Length));



    return new RijndaelManaged

    {

       Mode = CipherMode.CBC,

       Padding = PaddingMode.Zeros,

       KeySize = 256, 

       BlockSize = 128, 

       Key = keyBytes,

       IV = ivKeyBytes

    };

}

So can help me to resolve this issue

---

My Answer:
The issue you are facing is likely due to the different padding modes used in PHP and .NET/C#. In your C# code, you are using PaddingMode.Zeros, while in PHP, the default padding mode is PKCS7.

To resolve this issue, you need to ensure that both PHP and C# are using the same padding mode. You can change the padding mode in your C# code to match the default padding mode used in PHP, which is PKCS7.

In your C# code, change the Padding mode to PKCS7:
csharp
return new RijndaelManaged
{
Mode = CipherMode.CBC,
Padding = PaddingMode.PKCS7,
KeySize = 256,
BlockSize = 128,
Key = keyBytes,
IV = ivKeyBytes
};


After making this change, try encrypting and decrypting the data again and see if the extra characters issue is resolved. This should ensure compatibility between the encryption and decryption processes in PHP and C#.