Diffie-Hillman key exchange and encryption implemetation in PHP

testEnc.php

<?php

class Encryption
{
    public const ALGORITHM = "ECDH";
    public const CURVE = "curve25519";

    public static function encrypt($sInput, $oSenderPrivateKey, $receiverPublicKey, $randomKeySender, $randomKeyReceiver)
    {
        $xorOfRandoms = self::XorOfRandom($randomKeySender, $randomKeyReceiver);

        $encryptionKey = self::generateEncryptionKey($xorOfRandoms, $oSenderPrivateKey, $receiverPublicKey);

        $iv = substr($xorOfRandoms, 0, -12);

        global $tag;

        $sResult = openssl_encrypt($sInput, 'aes-256-gcm', $encryptionKey, 0, $iv, $tag);

        return $sResult;
    }

    public static function decrypt($sInput, $oReceiverPrivateKey, $senderPublicKey, $randomKeySender, $randomKeyReceiver)
    {
        $xorOfRandoms = self::XorOfRandom($randomKeySender, $randomKeyReceiver);

        $encryptionKey = self::generateEncryptionKey($xorOfRandoms, $oReceiverPrivateKey, $senderPublicKey);

        $iv = substr($xorOfRandoms, 0, -12);

        global $tag;

        $sResult = openssl_decrypt($sInput, 'aes-256-gcm', $encryptionKey, 0, $iv, $tag);

        return $sResult;
    }

    public static function generateEncryptionKey($xorOfRandoms, $oPrivateKey, $sPublicKey)
    {
        $sPrivateKey = openssl_pkey_get_private($oPrivateKey);
        $sSharedKey = openssl_dh_compute_key(base64_decode($sPublicKey), $sPrivateKey);

        $salt = substr($xorOfRandoms, 0, 20);

        $encryptionKey = hash_hkdf('sha256', $sSharedKey, 32, 'aes-256-gcm', $salt);

        return $encryptionKey;
    }

    public static function generateKey()
    {
        $configargs = array();
        $configargs['p'] = hex2bin('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');
        $configargs['g'] = hex2bin('02');

        return openssl_pkey_new([
            'curve' => Encryption::CURVE,
            'digest_alg' => Encryption::ALGORITHM,
            'dh' => $configargs
        ]);
    }



    public function XorOfRandom($randomKeySender, $randomKeyReceiver)
    {
        $result = base64_decode($randomKeySender) xor base64_decode($randomKeyReceiver);
        return base64_encode($result);
    }
}



$oReceiversKeyPair = Encryption::generateKey();
$sReceiversPublicKey = openssl_pkey_get_details($oReceiversKeyPair);

$oSendersKeyPair = Encryption::generateKey();
$sSendersPublicKey = openssl_pkey_get_details($oSendersKeyPair);


$receiverPublicKey = base64_encode($sReceiversPublicKey['dh']['pub_key']);
$senderPublicKey = base64_encode($sSendersPublicKey['dh']['pub_key']);
var_dump("receiverPublicKey:", $receiverPublicKey);
var_dump("senderPublicKey:", $senderPublicKey);

$randomKeySender = base64_encode(random_bytes(32));
$randomKeyReceiver = base64_encode(random_bytes(32));
var_dump("randomKeySender:", $randomKeySender);
var_dump("randomKeyReceiver:", $randomKeyReceiver);

$sDataToTest = "test data goes here";

($sEncrypted = Encryption::encrypt(
    $sDataToTest,
    $oSendersKeyPair,
    $receiverPublicKey,
    $randomKeySender,
    $randomKeyReceiver
));

var_dump("sEncrypted:", $sEncrypted);


($sDecrypted = Encryption::decrypt(
    $sEncrypted,
    $oReceiversKeyPair,
    $senderPublicKey,
    $randomKeySender,
    $randomKeyReceiver
));
var_dump("sDecrypted:", $sDecrypted);