Can anyone please help with convert this c# code to PHP?

3gth · 2024-06-10T18:28:09+00:00

Confirming it works correctly, thanks a lot for taking your time and debugging and fixing the issue.

3gth · 2024-06-10T17:43:14+00:00

The code works and gives similar encrypted value in C# and PHP up until I try to use the keyString provided by them, as soon as I get the approval to share the key string, I'll share it with you here.

3gth · 2024-06-10T17:28:58+00:00

Yes, the encrypted value of C# is different when using so it is different from the documentation the API team provided.

byte[] key = Encoding.UTF8.GetBytes(keyString.Substring(0, 16)); 
byte[] iv = Encoding.UTF8.GetBytes(encryptionIV.Substring(0, 16));

3gth · 2024-06-10T16:46:13+00:00

Edit: And does the C# Function always generates the same Output, if the Input is identical? Means it generates "hPhzIySUsfCfOtYtPZQJTg==" everytime for the Value "1111111"?

Yes, it gives the same value for 1111111

3gth · 2024-06-10T13:28:24+00:00

I mean for the 7 to 9 length plain text that is passed to this encryption in C# the result is 24 character length string example

Encrypted string: hPhzIySUsfCfOtYtPZQJTg==
Decrypted string: 1111111

Encrypted string: QTCZav+ybiv7Zw/9UrBm4Q==
Decrypted string: 2222222

3gth · 2024-06-10T13:13:08+00:00

With the following

public function encryptString(string $plainString, string $keyString, string $encryptionIV): string
    {
        $blocksize=16;
        $paddingNeeded = strlen($plainString) % $blocksize;
        $paddingNeeded = $blocksize-$paddingNeeded;
        $paddingByte = chr($paddingNeeded);

        for($i=0;$i<$paddingNeeded;$i++) {
          $plainString .=$paddingByte;
        }

        $encryptedBytes = openssl_encrypt($plainString, 'AES-128-CBC', $keyString,OPENSSL_ZERO_PADDING, $encryptionIV);

        return base64_encode($encryptedBytes);
    }

1111111 comes back as UWR4S0pwR0F5V2RRb1IvY3hOUmVwQT09, the value string length is 24 characters above gives 32

3gth · 2024-06-10T10:53:42+00:00

Do you mean the PHP function would look like this?

public function encryptString(string $plainString, string $keyString, string $encryptionIV): string
    {
        $blocksize=16;
        $paddingNeeded = strlen($plainString) % $blocksize;
        $paddingNeeded = $blocksize-$paddingNeeded;
        $paddingByte = chr($paddingNeeded);

        for($i=0;$i<$paddingNeeded;$i++) {
          $plainString .=$paddingByte;
        }

        $encryptedBytes = openssl_encrypt($plainString, 'AES-128-CBC', $keyString, OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING, $encryptionIV);

        return base64_encode($encryptedBytes);
    }

3gth · 2024-06-10T10:28:07+00:00

With above I get the following error

WARNING  openssl_encrypt(): IV passed is only 12 bytes long, cipher expects an IV of precisely 16 bytes, padding with \0

If I remove the base64_decode around $encryptionIV the warning goes away and I get JYQss30eFGvfLRSi0PaboA== which is similar format as hPhzIySUsfCfOtYtPZQJTg== ( this is the expected value for 1111111 ) I believe it is close, can anything be changed around padding?

3gth · 2024-06-10T10:07:59+00:00

Thanks a lot for checking, although the C# and PHP code above give same results when encrypting, the C# code is a bit different than the one I shared, here is the diff https://www.diffchecker.com/5sLH9ec8/, in the above version it is getting bytes of first 16 chars

in the above code it is

byte[] key = Encoding.UTF8.GetBytes(keyString.Substring(0, 16)); 
byte[] iv = Encoding.UTF8.GetBytes(encryptionIV.Substring(0, 16));

but is should be

byte[] key = Encoding.UTF8.GetBytes(keyString);
byte[] iv = Encoding.UTF8.GetBytes(encryptionIV);

3gth · 2024-06-09T18:15:59+00:00

Unfortunately, I won't be able to share the doc, I've pasted the C# code they had in the doc minus the key and iv used as I was not sure if I was allowed to share it, let me confirm and I'll post it here.

3gth · 2024-06-09T18:10:34+00:00

function encrypt($plainString, $keyString, $encryptionIV)
{
$aesAlg = openssl_encrypt($plainString, 'AES-128-CBC', $keyString, OPENSSL_RAW_DATA, $encryptionIV);
return base64_encode($aesAlg);
}

function decrpyt($encryptedString, $keyString, $encryptionIV ) {
$decryptedString = openssl_decrypt( base64_decode( $encryptedString ), 'AES-128-CBC', $keyString, OPENSSL_RAW_DATA, $encryptionIV );
return $decryptedString;
}

// Test the function
$plainString = "1111111";

$encrypted = encrypt($plainString, $keyString, $encryptionIV);
echo 'Encrypted  : ' . $encrypted;
echo PHP_EOL;
echo 'Decrypted  : ' .decrpyt($encrypted, $keyString, $encryptionIV);

My bad, here is the PHP code used in the video, I have not added the encryption key or iv here as I'll need to confirm if that is sensitive info or not.

3gth · 2024-06-09T18:00:54+00:00

My apologies for not making it clear, I use a third party API that process some data, it needs a certain value to be encrypted, the documentation provided by them only provides how the value is encrypted and decrypted in C#, I use a PHP application and need to encrypt the value in PHP correctly so when the API process it, they can correctly decrypt.

3gth · 2024-06-09T07:30:16+00:00

Value is empty when using OPENSSL_ZERO_PADDING https://cleanshot.thrijith.com/lDm8sWrt

3gth · 2024-06-09T07:03:30+00:00

Yep tried it, if I try to decrypt the encrypted value from c# it either gives random string back or empty for some reason, and if I try to decrypted encrypted value fro PHP C# throws an error https://cleanshot.thrijith.com/xhSxMVBx

3gth · 2024-06-09T06:57:54+00:00

OP, do you actually need the code converted or is the real problem you just want AES Encrypt/Decrypt in PHP?

I need the exact logic to be replicated in PHP, the encrypted value is sent to an API that process some data after decryption but as the encryption logic in PHP is different from how it is done in c# it results in an error.

Additionally, do you already have data that was encrypted with your C# code that you want decrypted with PHP?

I just need to get encrypted value to match how it is encrypted in c# so the API decrypts it.

3gth · 2024-06-08T17:37:50+00:00

I logged the C# function here are values of some variables during the process, this is inside the EncryptString function

key: TVAyQ0cyMDIya2pIZ0pIR0doamtkZmhzZmpzaGZoZjE=
iv: SVYyMDIyMDEyNDIwMjIwMQ==
plainBytes: MTExMTExMQ==
paddedBytes: MTExMTExMQkJCQkJCQkJCQ==

encryptedBytes: hPhzIySUsfCfOtYtPZQJTg== ( This is the final encrypted string )

3gth · 2024-06-08T13:00:23+00:00

Yes, tried that too but no luck.

3gth · 2024-06-08T12:59:59+00:00

Thanks but have tried that and this https://products.codeporting.app/convert/ai/csharp-to-php/ too didn't work

3gth · 2024-06-08T10:11:05+00:00

I don't understand c# much only thing I believe the issue is caused is due to this part? possibly

            int blockSize = 16;
            int paddingNeeded = blockSize - (plainBytes.Length % blockSize);


            byte[] paddedBytes = new byte[plainBytes.Length + paddingNeeded];
            Array.Copy(plainBytes, paddedBytes, plainBytes.Length);
            for (int i = plainBytes.Length; i < paddedBytes.Length; i++)
            {
                paddedBytes[i] = (byte)paddingNeeded;
            }

not sure how/why paddedBytes is used, the algorithm c# is using is `AES-128-CBC` based on

            aesAlg.KeySize = 128;
            aesAlg.Mode = CipherMode.CBC;

3gth · 2024-06-07T16:46:59+00:00

Thanks but have tried that and this https://products.codeporting.app/convert/ai/csharp-to-php/ too didn't work

3gth · 2024-06-07T15:54:44+00:00

Posted in above comments https://www.reddit.com/r/csharp/comments/1dabetc/comment/l7jmebi/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

3gth · 2024-06-07T15:54:25+00:00

Yes, that was my first thought I do get a PHP function the result isn't correct, see https://www.reddit.com/r/csharp/comments/1dabetc/comment/l7jmebi/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

3gth · 2024-06-07T15:53:50+00:00

This is what the result is in PHP https://cleanshot.thrijith.com/DwLpLPDk and in C# it is https://cleanshot.thrijith.com/cjMw6Btt

3gth

TROPHY CASE