I am involved in the development of two system communication projects. The Java-based system on the other side requires the transmitted content to be encrypted using AES. Our system is currently based on .NET Framework 7 (NET7). I am attempting to decrypt the content from the other party using C#. I tried implementing the algorithm using the “BouncyCastle.Cryptography” framework, attempting to mimic the Java coding style, but unfortunately, I was unsuccessful. I have been struggling with this issue for a few days and have decided to seek help here.

Here is a snippet of the java implementation:

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Base64;
public class AESUtil {
    private static final String KEY_ALGORITHM_AES = "AES";
    private static final String DEFAULT_CIPHER_ALGORITHM = "AES/GCM/NoPadding";
    private static final String CHARSET = "UTF-8";
    public static String aesEncrypt(String content, String encryptPass) {
        try {
            byte[] iv = new byte[12];
            SecureRandom secureRandom = new SecureRandom();
            secureRandom.nextBytes(iv);
            byte[] contentBytes = content.getBytes(CHARSET);
            Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);
            GCMParameterSpec params = new GCMParameterSpec(128, iv);
            cipher.init(Cipher.ENCRYPT_MODE, getSecretKey(encryptPass), params);
            byte[] encryptData = cipher.doFinal(contentBytes);
            assert encryptData.length == contentBytes.length + 16;
            byte[] message = new byte[12 + contentBytes.length + 16];
            System.arraycopy(iv, 0, message, 0, 12);
            System.arraycopy(encryptData, 0, message, 12, encryptData.length);
            return Base64.getEncoder().encodeToString(message);
        } catch (Exception e) {

        }
        return null;
    }

    public static String aesDecrypt(String base64Content, String encryptPass) {
        try {
            byte[] content = Base64.getDecoder().decode(base64Content);
            if (content.length < 12 + 16) {
                throw new IllegalArgumentException();
            }
            GCMParameterSpec params = new GCMParameterSpec(128, content, 0, 12);
            Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);
            cipher.init(Cipher.DECRYPT_MODE, getSecretKey(encryptPass), params);
            byte[] decryptData = cipher.doFinal(content, 12, content.length - 12);
            return new String(decryptData, CHARSET);
        } catch (Exception e) {
            System.out.println("error：" + e.getMessage());
        }
        return null;
    }

    private static SecretKeySpec getSecretKey(String encryptPass) throws NoSuchAlgorithmException {
        KeyGenerator kg = KeyGenerator.getInstance(KEY_ALGORITHM_AES);
        SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
        secureRandom.setSeed(encryptPass.getBytes());
        kg.init(128, secureRandom);
        SecretKey secretKey = kg.generateKey();
        return new SecretKeySpec(secretKey.getEncoded(), KEY_ALGORITHM_AES);
    }
}

I would like the C# code I write to be able to achieve mutual encryption and decryption with the Java version