c# – System.Security.Cryptography vs PCLCrypto

我们正在努力在我们的系统中挖掘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.

见下面的代码：
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,plainTextBuffer.Length);
    symmetricAlgorithm.Clear();

    return Convert.ToBase64String(cipherBuffer);
}


 public static string SymmetricDecrypt(this string cipherText,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,cipherTextBuffer.Length);
        symmetricAlgorithm.Clear();

        return Encoding.Default.GetString(plainTextBuffer);
    }

使用PCLCrypto解密

public static string SymmetricDecrypt(this string cipherText,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,cipherTextBuffer.Length);
    return UTF8Encoding.UTF8.GetString(plainTextBuffer,plainTextBuffer.Length);
}

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

救命！

解决方法

这听起来像填充问题.

查看.NET中基类SymmetricAlgorithm的源代码,它是AesCryptoServiceProvider的基础,默认填充是PaddingMode.PKCS7.您似乎没有定义填充模式,因此我认为默认仍然适用.

虽然我以前没有使用过PCLCrypto库,但是快速浏览一下github有几种AesEcb算法：AesEcb和AesEcbPkcs7.从AesEcb的名称缺少填充模式将意味着它没有填充(因此没有删除任何填充),这将相当于.NET库中的PaddingMode.None.

尝试在PCLCrypto中使用PCLCrypto.SymmetricAlgorithm.AesEcbPkcs7算法,看看是否删除了在输出结尾处看到的填充.

更新

我刚刚对此进行了测试,它似乎正常工作并删除了您将看到的填充：

public static string SymmetricDecrypt(this string cipherText,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,plainTextBuffer.Length);
}

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