对称加密循环冗余校验

Question

在写入数据库之前，我需要加密一些数据，从DB读取数据时需要解密。

我使用了本指南中提供的代码：在通用Windows应用程序中加密和解密数据

每当我试图解密时，我就会得到错误：

数据错误(循环冗余检查)。(HRESULT例外: 0x80070017)

我认为这是因为密钥是不同的，因为我实例化了SymmetricEncryptionHelper对象一次用于加密，另一次用于解密。为了解决这一问题，我将类更改为单例，但仍然得到了相同的错误：

public class SymmetricEncryptionHelper
{
    private readonly IBuffer randomBuffer;
    private readonly IBuffer randomBufferCBC;
    private readonly CryptographicKey cryptographicKey;
    private readonly string algorithmName;
    private readonly SymmetricKeyAlgorithmProvider cryptingProvider;

    private static SymmetricEncryptionHelper _instance;

    public static SymmetricEncryptionHelper Instance
    {
        get
        {
            if (_instance == null)
            {
                _instance = new SymmetricEncryptionHelper();
            }
            return _instance;
        }
    }


    /// <summary>
    /// Instantiate with a random generated buffer (not an option if
    /// you want to persist the encryption to disk)
    /// </summary>
    private SymmetricEncryptionHelper()
    {
        algorithmName = SymmetricAlgorithmNames.AesEcbPkcs7;
        cryptingProvider = SymmetricKeyAlgorithmProvider.OpenAlgorithm(algorithmName);
        randomBuffer = CryptographicBuffer.GenerateRandom(cryptingProvider.BlockLength);
        randomBufferCBC = null;
        cryptographicKey = cryptingProvider.CreateSymmetricKey(randomBuffer);
    }

    /// <summary>
    /// Instantiate with a custom generated buffer (good for
    /// persisting the encryption to disk)
    /// </summary>
    /// <param name="randomBuffer">The custom generated buffer</param>
    private SymmetricEncryptionHelper(IBuffer randomBuffer)
        : this()
    {
        this.randomBuffer = randomBuffer;
        cryptographicKey = cryptingProvider.CreateSymmetricKey(randomBuffer);
    }
    /// <summary>
    /// Instantiate with a custom generated buffer (good for
    /// persisting the encryption to disk) and with a custom
    /// generated CBC buffer (is using CBC algorithms)
    /// </summary>
    /// <param name="randomBuffer">The custom generated buffer</param>
    /// <param name="randomBufferCBC">The custom generated CBC buffer</param>
    private SymmetricEncryptionHelper(IBuffer randomBuffer, IBuffer randomBufferCBC)
        : this(randomBuffer)
    {
        this.randomBufferCBC = randomBufferCBC;
    }

    private bool IsMultipleOfBlockLength(IBuffer binaryData)
    {
        return (binaryData.Length % cryptingProvider.BlockLength) != 0;
    }
    /// <summary>
    /// Encrypts a given string
    /// </summary>
    /// <param name="data">Data to be encrypted</param>
    /// <returns>An encrypted string in Unicode</returns>
    public string Encrypt(string data)
    {
        if (string.IsNullOrEmpty(data))
        {
            return data;
        }

        var binaryData = Encoding.Unicode.GetBytes(data).AsBuffer();
        if (!algorithmName.Contains("PKCS7") && IsMultipleOfBlockLength(binaryData))
            throw new Exception("Message buffer length must be multiple of block length !!");
        var encryptedBinaryData = CryptographicEngine.Encrypt(cryptographicKey, binaryData, randomBufferCBC);
        return Encoding.Unicode.GetString(encryptedBinaryData.ToArray());
    }
    /// <summary>
    /// Decrypts a string in Unicode
    /// </summary>
    /// <param name="encryptedData">An encrypted string in Unicode</param>
    /// <returns>The decrypted string in Unicode</returns>
    public string Decrypt(string encryptedData)
    {
        if (string.IsNullOrEmpty(encryptedData))
        {
            return encryptedData;
        }

        try
        {
            var encryptedBinaryData = Encoding.Unicode.GetBytes(encryptedData).AsBuffer();
            var decryptedData = CryptographicEngine.Decrypt(cryptographicKey, encryptedBinaryData, randomBufferCBC);
            return Encoding.Unicode.GetString(decryptedData.ToArray());
        }
        catch (Exception ex)
        {
            return null;
        }
    }

}

有人能看到我哪里出错了吗?我在谷歌上搜索了错误，但似乎找不到对我有用的答案。

此外，一旦应用程序关闭，我将失去钥匙，那么这里的最佳实践是什么？我应该把密钥保存在PasswordVault中吗？

Answer 1

不要信任互联网上的随机代码。你得知道你在做什么。欧洲央行模式加密对于文本消息来说是不安全的，而且大多数其他密码操作都是不安全的。

您的问题是直接依赖于加密方法中生成的密文的解码(使用Encoding.Unicode.GetString，微软的坏名称UTF-16 on )。现在，密文总是包含随机字节。这些字节对并不总是构成有效的UTF-16 of编码字符。因此，通常这些被忽略在严格的密文或他们被一个替代字符取代。

显然，如果引入了替代字符，那么这个特定的密文块将被解密成一个随机数据块，从而使您的CRC检查失败。

如果出于某种原因需要将密文显示为文本，则base64对其进行编码。