如何在Dart中实现与C# RijndaelManaged一致的字符串加密解密？

我有一段用RijndaelManaged实现的C#字符串加密解密代码，需要在Flutter（Dart）中复刻相同逻辑，让Dart加密的内容能被C#正常解密。试了多个包都没成功，当前Dart代码加密的密文在C#解密时总是报*“Padding is invalid and cannot be removed.”*错误。

C# 实现代码 #

public static string key = Environment.GetEnvironmentVariable("ENCR_KEY");
private const int Keysize = 256;
private const int DerivationIterations = 100;

public string Encrypt(string plainText)
{  
    var saltStringBytes = Generate256BitsOfRandomEntropy();
    var ivStringBytes = Generate256BitsOfRandomEntropy();
    var plainTextBytes = Encoding.UTF8.GetBytes(plainText);
    using (var password = new Rfc2898DeriveBytes(key, saltStringBytes, DerivationIterations))
    {
        var keyBytes = password.GetBytes(Keysize / 8);
        using (var symmetricKey = new RijndaelManaged())
        {
            symmetricKey.BlockSize = 128;
            symmetricKey.Mode = CipherMode.CBC;
            //symmetricKey.Padding = PaddingMode.PKCS7;
            using (var encryptor = symmetricKey.CreateEncryptor(keyBytes, ivStringBytes))
            {
                using (var memoryStream = new MemoryStream())
                {
                    using (var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                    {
                        cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
                        cryptoStream.FlushFinalBlock();
                        var cipherTextBytes = saltStringBytes;
                        cipherTextBytes = cipherTextBytes.Concat(ivStringBytes).ToArray();
                        cipherTextBytes = cipherTextBytes.Concat(memoryStream.ToArray()).ToArray();
                        memoryStream.Close();
                        cryptoStream.Close();
                        return Convert.ToBase64String(cipherTextBytes);
                    }
                }
            }
        }
    }
}

private static byte[] Generate256BitsOfRandomEntropy()
{
    var randomBytes = new byte[16]; 
    using (var rngCsp = new RNGCryptoServiceProvider())
    {
        rngCsp.GetBytes(randomBytes);
    }
    return randomBytes;
}

public string Decrypt(string cipherText)
{
    string password = key;
    byte[] cipherBytes = Convert.FromBase64String(cipherText);
    using (Aes encryptor = Aes.Create())
    {
        var salt = cipherBytes.Take(16).ToArray();
        var iv = cipherBytes.Skip(16).Take(16).ToArray();
        var encrypted = cipherBytes.Skip(32).ToArray();
        Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(password, salt, 100);
        encryptor.Key = pdb.GetBytes(32);
        encryptor.Padding = PaddingMode.PKCS7;
        encryptor.Mode = CipherMode.CBC;
        encryptor.IV = iv;
        using (MemoryStream ms = new MemoryStream(encrypted))
        {
            using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Read))
            {
                using (var reader = new StreamReader(cs, Encoding.UTF8))
                {
                    return reader.ReadToEnd();
                }
            }
        }
    }
}

Dart 当前实现代码 #

import 'dart:convert';
import 'package:pointycastle/block/aes_fast.dart';
import 'dart:typed_data';
import 'package:pointycastle/export.dart';
import 'package:pointycastle/key_derivators/pbkdf2.dart';
import 'package:pointycastle/paddings/pkcs7.dart';
import 'package:pointycastle/pointycastle.dart';

const KEY_SIZE = 32; // 32 byte key for AES-256
const ITERATION_COUNT = 2;
const SALT = "XXXXXXXXXXXXXXXXX";
const INITIAL_VECTOR = "ZZZZZZZZZZZZZZZZ";
const PASS_PHRASE = "YYYYYYYYYYYYYYYYYYY";

Future<String> cryptString(String text) async {
  String encryptedString = "";

  final mStrPassPhrase = toUtf8(PASS_PHRASE);

  encryptedString = AesHelperMethod2.encrypt(
    mStrPassPhrase,
    toUtf8(text),
    mode: AesHelperMethod2.CBC_MODE,
  );

  return encryptedString;
}

Future<String> decryptString(String text) async {
  String decryptedString = "";

  final mStrPassPhrase = toUtf8(PASS_PHRASE);

  decryptedString = AesHelperMethod2.decrypt(mStrPassPhrase, toUtf8(text),
      mode: AesHelperMethod2.CBC_MODE);

  return decryptedString;
}

///MARK: AesHelper class
class AesHelperMethod2 {
  static const CBC_MODE = 'CBC';
  static const CFB_MODE = 'CFB';

  static Uint8List deriveKey(dynamic password,
      {String salt = '',
      int iterationCount = ITERATION_COUNT,
      int derivedKeyLength = KEY_SIZE}) {
    if (password == null || password.isEmpty) {
      throw new ArgumentError('password must not be empty');
    }

    if (password is String) {
      password = createUint8ListFromString(password);
    }

    Uint8List saltBytes = createUint8ListFromString(salt);
    Pbkdf2Parameters params =
        new Pbkdf2Parameters(saltBytes, iterationCount, derivedKeyLength);
    KeyDerivator keyDerivator =
        new PBKDF2KeyDerivator(new HMac(new SHA1Digest(), 64));
    keyDerivator.init(params);

    return keyDerivator.process(password);
  }

  static Uint8List pad(Uint8List src, int blockSize) {
    var pad = new PKCS7Padding();
    pad.init(null);

    int padLength = blockSize - (src.length % blockSize);
    var out = new Uint8List(src.length + padLength)..setAll(0, src);
    pad.addPadding(out, src.length);

    return out;
  }

  static Uint8List unpad(Uint8List src) {
    var pad = new PKCS7Padding();
    pad.init(null);

    int padLength = pad.padCount(src);
    int len = src.length - padLength;

    return new Uint8List(len)..setRange(0, len, src);
  }

  static String encrypt(String password, String plaintext,
      {String mode = CBC_MODE}) {
    String salt = toASCII(SALT);
    Uint8List derivedKey = deriveKey(password, salt: salt);
    KeyParameter keyParam = new KeyParameter(derivedKey);
    BlockCipher aes = new AESFastEngine();

    var ivStr = toASCII(INITIAL_VECTOR);
    Uint8List iv = createUint8ListFromString(ivStr);

    BlockCipher cipher;
    ParametersWithIV params = new ParametersWithIV(keyParam, iv);
    switch (mode) {
      case CBC_MODE:
        cipher = new CBCBlockCipher(aes);
        break;
      case CFB_MODE:
        cipher = new CFBBlockCipher(aes, aes.blockSize);
        break;
      default:
        throw new ArgumentError('incorrect value of the "mode" parameter');
        break;
    }
    cipher.init(true, params);

    Uint8List textBytes = createUint8ListFromString(plaintext);
    Uint8List paddedText = pad(textBytes, aes.blockSize);
    Uint8List cipherBytes = _processBlocks(cipher, paddedText);
    final enc = base64.encode(cipherBytes);
    print("enc : " "$enc");
    return base64.encode(cipherBytes);
  }

  static String decrypt(String password, String ciphertext,
      {String mode = CBC_MODE}) {
    String salt = toASCII(SALT);
    Uint8List derivedKey = deriveKey(password, salt: salt);
    KeyParameter keyParam = new KeyParameter(derivedKey);
    BlockCipher aes = new AESFastEngine();

    var ivStr = toASCII(INITIAL_VECTOR);
    Uint8List iv = createUint8ListFromString(ivStr);
    Uint8List cipherBytesFromEncode = base64.decode(ciphertext);

    Uint8List cipherIvBytes =
        new Uint8List(cipherBytesFromEncode.length + iv.length)
          ..setAll(0, iv)
          ..setAll(iv.length, cipherBytesFromEncode);

    BlockCipher cipher;

    ParametersWithIV params = new ParametersWithIV(keyParam, iv);
    switch (mode) {
      case CBC_MODE:
        cipher = new CBCBlockCipher(aes);
        break;
      case CFB_MODE:
        cipher = new CFBBlockCipher(aes, aes.blockSize);
        break;
      default:
        throw new ArgumentError('incorrect value of the "mode" parameter');
        break;
    }
    cipher.init(false, params);

    int cipherLen = cipherIvBytes.length - aes.blockSize;
    Uint8List cipherBytes = new Uint8List(cipherLen)
      ..setRange(0, cipherLen, cipherIvBytes, aes.blockSize);
    Uint8List paddedText = _processBlocks(cipher, cipherBytes);
    Uint8List textBytes = unpad(paddedText);

    return new String.fromCharCodes(textBytes);
  }

  static Uint8List _processBlocks(BlockCipher cipher, Uint8List inp) {
    var out = new Uint8List(inp.lengthInBytes);

    for (var offset = 0; offset < inp.lengthInBytes;) {
      var len = cipher.processBlock(inp, offset, out, offset);
      offset += len;
    }

    return out;
  }
}

///MARK: HELPERS
Uint8List createUint8ListFromString(String s) {
  Uint8List ret = Uint8List.fromList(s.codeUnits);

  return ret;
}

String toUtf8(value) {
  var encoded = utf8.encode(value);
  var decoded = utf8.decode(encoded);
  return decoded;
}

String toASCII(value) {
  var encoded = ascii.encode(value);
  var decoded = ascii.decode(encoded);
  return decoded;
}

内容的提问来源于stack exchange，提问作者Ajay AV