System.Security.Cryptography与PCLCrypto

Question

我们正在系统中删除大量共享功能并将其移植到PCL库中.我在使用PCLCrypto时遇到了问题.我正在我们的数据库中获取一些现有数据,并尝试使用相同的算法对其进行解密.我得到了值,但最后有16个额外的字节只是垃圾.

请参阅下面的代码: 使用System.Security.Cryptography的旧算法

public static string SymmetricEncrypt(this string plaintext, string key, SymmetricAlgorithm algorithm)
{
    byte[] keyBuffer = Convert.FromBase64String(key.Hash(HashAlgorithm.MD5));
    byte[] plainTextBuffer = Encoding.UTF8.GetBytes(plaintext);

   var symmetricAlgorithm = new AesCryptoServiceProvider();
    symmetricAlgorithm.Key = keyBuffer;
    symmetricAlgorithm.Mode = CipherMode.ECB;

    var encryptor = symmetricAlgorithm.CreateEncryptor();
    byte[] cipherBuffer = encryptor.TransformFinalBlock(plainTextBuffer, 0, plainTextBuffer.Length);
    symmetricAlgorithm.Clear();

    return Convert.ToBase64String(cipherBuffer);
}


 public static string SymmetricDecrypt(this string cipherText, string key, SymmetricAlgorithm algorithm)
    {
        byte[] keyBuffer = Convert.FromBase64String(key.Hash(HashAlgorithm.MD5));
        byte[] cipherTextBuffer = Convert.FromBase64String(cipherText);
        var symmetricAlgorithm = new AesCryptoServiceProvider();
        symmetricAlgorithm.Key = keyBuffer;
        symmetricAlgorithm.Mode = CipherMode.ECB;

        var decryptor = symmetricAlgorithm.CreateDecryptor();
        byte[] plainTextBuffer = decryptor.TransformFinalBlock(cipherTextBuffer, 0, cipherTextBuffer.Length);
        symmetricAlgorithm.Clear();

        return Encoding.Default.GetString(plainTextBuffer);
    }

使用PCLCrypto解密

public static string SymmetricDecrypt(this string cipherText, string key, SymmetricAlgorithm algorithm) {
    byte[] keyBuffer = Convert.FromBase64String(key.Hash(HashAlgorithm.MD5));
    byte[] cipherTextBuffer = Convert.FromBase64String(cipherText);

    ISymmetricKeyAlgorithmProvider symmetricAlgorithm = WinRTCrypto.SymmetricKeyAlgorithmProvider.OpenAlgorithm(PCLCrypto.SymmetricAlgorithm.AesEcb);

    var symmetricKey = symmetricAlgorithm.CreateSymmetricKey(keyBuffer);
    var decryptor = WinRTCrypto.CryptographicEngine.CreateDecryptor(symmetricKey);
   byte[] plainTextBuffer = decryptor.TransformFinalBlock(cipherTextBuffer, 0, cipherTextBuffer.Length);
    return UTF8Encoding.UTF8.GetString(plainTextBuffer, 0, plainTextBuffer.Length);
}

使用旧版本:plainTextBuffer是16个字节,新版本是32个字节.

救命!

Answer 1

这听起来像是一个填充问题。

查看.NET中基类SymmetricAlgorithm的源代码，它是AesCryptoServiceProvider的基础，默认的填充是PaddingMode.PKCS7。您似乎没有定义填充模式，所以我假设默认值仍然适用。

虽然我之前没有使用过 PCLCrypto 库，但快速浏览一下 github 后发现有几个 AesEcb 算法：AesEcb 和 AesEcbPkcs7。AesEcb 名称中缺少填充模式对我来说意味着它没有填充（因此没有删除任何填充），这相当于 .NET 库中的 PaddingMode.None。

尝试在 PCLCrypto 中使用 PCLCrypto.SymmetricAlgorithm.AesEcbPkcs7 算法，看看这是否会删除您在输出末尾看到的填充。

更新

我刚刚对此进行了测试，它似乎工作正常并删除了您将看到的填充：

public static string SymmetricDecrypt(this string cipherText, string key, SymmetricAlgorithm algorithm) {
    byte[] keyBuffer = Convert.FromBase64String(key.Hash(HashAlgorithm.MD5));
    byte[] cipherTextBuffer = Convert.FromBase64String(cipherText);

    ISymmetricKeyAlgorithmProvider symmetricAlgorithm = WinRTCrypto.SymmetricKeyAlgorithmProvider.OpenAlgorithm(PCLCrypto.SymmetricAlgorithm.AesEcbPkcs7);

    var symmetricKey = symmetricAlgorithm.CreateSymmetricKey(keyBuffer);
    var decryptor = WinRTCrypto.CryptographicEngine.CreateDecryptor(symmetricKey);
   byte[] plainTextBuffer = decryptor.TransformFinalBlock(cipherTextBuffer, 0, cipherTextBuffer.Length);
    return UTF8Encoding.UTF8.GetString(plainTextBuffer, 0, plainTextBuffer.Length);
}

唯一的变化是将算法从 PCLCrypto.SymmetricAlgorithm.AesEcb 更改为 PCLCrypto.SymmetricAlgorithm.AesEcbPkcs7