要解密的数据长度无效

我正在尝试解密字节数组，但出现此错误：

要解密的数据长度无效。

此时发生错误：

int decryptedByteCount = cryptoStream
                        .Read(plainTextBytes, 0, plainTextBytes.Length);

这是完整的代码

public static byte[] Decrypt(byte[] encryptedBytes, string key) {
    string initVector = "@1B2c3D4e5F6g7H8";
    string saltValue = "s@1tValue";
    string passPhrase = key;//"s@1tValue";
    string hashAlgorithm = "SHA1";
    int passwordIterations = 2;
    int keySize = 128;
    // Convert strings defining encryption key characteristics into byte
    // arrays. Let us assume that strings only contain ASCII codes.
    // If strings include Unicode characters, use Unicode, UTF7, or UTF8
    // encoding.
    byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector);
    byte[] saltValueBytes = Encoding.ASCII.GetBytes(saltValue);
    // Convert our ciphertext into a byte array.
    byte[] cipherTextBytes = encryptedBytes;
    // First, we must create a password, from which the key will be 
    // derived. This password will be generated from the specified 
    // passphrase and salt value. The password will be created using
    // the specified hash algorithm. Password creation can be done in
    // several iterations.
    PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, saltValueBytes, hashAlgorithm, passwordIterations);
    // Use the password to generate pseudo-random bytes for the encryption
    // key. Specify the size of the key in bytes (instead of bits).
    byte[] keyBytes = password.GetBytes(keySize / 8);
    // Create uninitialized Rijndael encryption object.
    TripleDESCryptoServiceProvider symmetricKey = new TripleDESCryptoServiceProvider();
    // It is reasonable to set encryption mode to Cipher Block Chaining
    // (CBC). Use default options for other symmetric key parameters.
    symmetricKey.Mode = CipherMode.CBC;
    // Generate decryptor from the existing key bytes and initialization 
    // vector. Key size will be defined based on the number of the key 
    // bytes.
    ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes);
    // Define memory stream which will be used to hold encrypted data.
    MemoryStream memoryStream = new MemoryStream(cipherTextBytes);
    // Define cryptographic stream (always use Read mode for encryption).
    CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
    // Since at this point we don't know what the size of decrypted data
    // will be, allocate the buffer long enough to hold ciphertext;
    // plaintext is never longer than ciphertext.
    byte[] plainTextBytes = new byte[cipherTextBytes.Length];
    // Start decrypting.
    int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
    // Close both streams.
    memoryStream.Close();
    cryptoStream.Close();
    // Convert decrypted data into a string. 
    // Let us assume that the original plaintext string was UTF8-encoded.
    string plainText = Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
    // Return decrypted string.   
    //return plainText;
    return plainTextBytes;
}

        MemoryStream fileStreamIn = new MemoryStream(buffer);
        ZipInputStream zipInStream = new ZipInputStream(fileStreamIn);
        ZipEntry entry = zipInStream.GetNextEntry();
        MemoryStream fileStreamOut = new MemoryStream();
        int size;
        byte[] bufferOut = new byte[buffer.Length];
        do {
            size = zipInStream.Read(bufferOut, 0, bufferOut.Length);
            fileStreamOut.Write(bufferOut, 0, size);
        } while (size > 0);
        zipInStream.Close();
        fileStreamOut.Close();
        fileStreamIn.Close();
        return bufferOut;