Javaで暗号化しC#で復号する

Javaで動くAndroidと.NETで動くAPIサーバーの認証のためにJava側で暗号化した文字列を.Net側で復号して認証処理を行うという仕組みを構築するために、Javaで暗号化するコード、C#で復号するコードを作りました。

Encrypt.java

    @TargetApi(Build.VERSION_CODES.O)
    @RequiresApi(api = Build.VERSION_CODES.O)
    public static String Encrypt(String text, String key)
            throws Exception {
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        byte[] keyBytes= new byte[16];
        byte[] b= key.getBytes(StandardCharsets.UTF_8);
        int len= b.length;
        if (len > keyBytes.length) len = keyBytes.length;
        System.arraycopy(b, 0, keyBytes, 0, len);
        SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");
        IvParameterSpec ivSpec = new IvParameterSpec(keyBytes);
        cipher.init(Cipher.ENCRYPT_MODE,keySpec,ivSpec);

        byte[] results = cipher.doFinal(text.getBytes(StandardCharsets.UTF_8));
        String result = Base64.getEncoder().encodeToString(results);
        return result;
    }

Decrypt.cs

       public static string Decrypt(string textToDecrypt, string key)
        {
            System.Text.UTF8Encoding encoding = new System.Text.UTF8Encoding();

            RijndaelManaged rijndaelCipher = new RijndaelManaged();
            rijndaelCipher.Mode = CipherMode.CBC;
            rijndaelCipher.Padding = PaddingMode.PKCS7;

            rijndaelCipher.KeySize = 0x80;
            rijndaelCipher.BlockSize = 0x80;

            //string decodedUrl = HttpUtility.UrlDecode(textToDecrypt);
            byte[] encryptedData = Convert.FromBase64String(textToDecrypt);
            byte[] pwdBytes = Encoding.UTF8.GetBytes(key);
            byte[] keyBytes = new byte[0x10];
            int len = pwdBytes.Length;
            if (len > keyBytes.Length)
            {
                len = keyBytes.Length;
            }
            Array.Copy(pwdBytes, keyBytes, len);
            rijndaelCipher.Key = keyBytes;
            rijndaelCipher.IV = keyBytes;
            byte[] plainText = rijndaelCipher.CreateDecryptor().TransformFinalBlock(encryptedData, 0, encryptedData.Length);
            return encoding.GetString(plainText);
        }