System.Security.Cryptography与PCLCrypto [英] System.Security.Cryptography vs PCLCrypto

问题描述

我们正在取消系统中的许多共享功能并将其移植到PCL库中.我在使用PCLCrypto时遇到问题.我正在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.我得到了返回的值，但最后有16个多余的字节只是垃圾.

We are in the process of gutting a lot of shared functionality in our system and porting it to PCL libraries. I am having an issue using PCLCrypto. I am taking some existing data in our database, and trying to decrypt it with the same algorithm. I get the value back, but there are 16 extra bytes at the end that are just garbage.

请参见下面的代码: 使用System.Security.Cryptography的旧算法

See Code below: Old Algorithm using System.Security.Cryptography

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为16字节，新版本为32字节.

Using the old version: plainTextBuffer is 16 bytes, new version it is 32 bytes.

帮助！

推荐答案

这听起来像是填充问题.

This sounds like a padding issue.

查看.NET中作为AesCryptoServiceProvider的基础的SymmetricAlgorithm基类的源，默认填充为PaddingMode.PKCS7.您似乎尚未定义填充模式，所以我认为默认设置仍然适用.

Looking at the source for the base class SymmetricAlgorithm in .NET, which is the base of the AesCryptoServiceProvider, the default padding is PaddingMode.PKCS7. You don't appear to have defined a padding mode, so I would assume the default still applies.

虽然我以前没有使用过PCLCrypto库，但快速浏览一下github时，有两种AesEcb算法:AesEcb和AesEcbPkcs7. AesEcb名称中不存在填充模式，这对我意味着它没有填充(因此没有删除任何填充)，这与.NET库中的PaddingMode.None等效.

Whilst I haven't used the PCLCrypto library before, having a quick look at github there are a couple of AesEcb algorithms: AesEcb and AesEcbPkcs7. The absence of a padding mode from the name of AesEcb would imply to me that it has no padding (and thus hasn't removed any padding), which would be the equivalent of PaddingMode.None in the .NET libraries.

尝试在PCLCrypto中使用PCLCrypto.SymmetricAlgorithm.AesEcbPkcs7算法，看看是否能消除在输出末尾看到的填充.

Try using the PCLCrypto.SymmetricAlgorithm.AesEcbPkcs7 algorithm in PCLCrypto and see if this removes the padding that you are seeing at the end of the output.

更新

Update

我刚刚对此进行了测试，它似乎可以正常工作，并删除了您将看到的填充:

I've just tested this, and it appears to work correctly and remove the padding you would be seeing:

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

The only change was changing the algorithm from PCLCrypto.SymmetricAlgorithm.AesEcb to PCLCrypto.SymmetricAlgorithm.AesEcbPkcs7

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