Salt中的什么导致它解密失败

Question

下面和 Fiddle 中的代码不是用于生产，而是用于教育目的。我不想解决任何问题，因为我有一个可行的解决方案。但是，我想知道为什么：

var password = "password";
var salt = Encoding.ASCII.GetBytes(password.Length.ToString());
var secret = new PasswordDeriveBytes(password, salt);

当上述实现时，在下面的方法FixedEncryptor 将起作用。

// Valid:
public static string FixedEncryptor(string content)
{
    var cipher = new RijndaelManaged();
    var plain = Encoding.Unicode.GetBytes(content);
    var key = new PasswordDeriveBytes(password, salt);
    using (var encrypt = cipher.CreateEncryptor(key.GetBytes(32), key.GetBytes(16)))
        using (var stream = new MemoryStream())
            using (var crypto = new CryptoStream(stream, encrypt, CryptoStreamMode.Write))
            {
                crypto.Write(plain, 0, plain.Length);
                crypto.FlushFinalBlock();
                return Convert.ToBase64String(stream.ToArray());
            }
}

但是，如果你实现：

var secret = new PasswordDeriveBytes("password",
     Encoding.ASCII.GetBytes("password"));

代码会突然产生：

运行时异常（第 70 行）：填充无效且不能 删除。

堆栈跟踪：

[System.Security.Cryptography.CryptographicException：填充是 无效且无法删除。] 在 Crypt.Decryptor（字符串内容）： Program.Main() 的第 70 行：第 17 行

如以下方法所示：

// Invalid:
public static string Encryptor(string content)
{
    var cipher = new RijndaelManaged();
    var plain = Encoding.Unicode.GetBytes(content);
    var key = new PasswordDeriveBytes("password", Encoding.ASCII.GetBytes("password"));
    using (var encrypt = cipher.CreateEncryptor(key.GetBytes(32), key.GetBytes(16)))
        using (var stream = new MemoryStream())
            using (var crypto = new CryptoStream(stream, encrypt, CryptoStreamMode.Write))
            {
                crypto.Write(plain, 0, plain.Length);
                crypto.FlushFinalBlock();
                return Convert.ToBase64String(stream.ToArray());
            }
}

那么为什么一个可以成功解密，而另一个不能正确解密并产生上述错误？

一个小例子的小提琴是here。

Answer 1

从您发布的代码示例中，您的问题来自您使用两种不同的盐这一事实。

在 FixedEncryptor 中你使用盐

Encoding.ASCII.GetBytes(password.Length.ToString());

编码为等于{ 56 } 的字节数组，这是因为Length 返回8 然后调用ToString() 返回字符串“8”，您将其转换为ascii 值56。

在 Encryptor 中你使用盐

Encoding.ASCII.GetBytes("password")

编码为等于{ 112, 97, 115, 115, 119, 111, 114, 100}的字节数组，即字符“p”、“a”、“s”、“s”、“w”、“o”、“r”的ascii值"和"d"。

您遇到的问题是您仅尝试在解密函数中使用{ 56 }，因此您的问题归结为您的加密函数和解密函数使用了两种不同的盐。

如果我创建一个新的Decrypter 以使用与Encryptor 相同的盐和密码，然后创建一个单独的FixedDecryptor 以匹配FixedEncryptor 的盐，一切都会正常工作

public class Program
{
    public static void Main()
    {
        var message = "Hello World!";
        var fixedCipherText = Crypt.FixedEncryptor(message);
        var cipherText = Crypt.Encryptor(message);
        Console.WriteLine(cipherText);
        Console.WriteLine(fixedCipherText);
        var plainText = Crypt.Decryptor(cipherText);
        var fixedPlainText = Crypt.FixedDecryptor(fixedCipherText);
        Console.WriteLine(plainText);
        Console.WriteLine(fixedPlainText);
    }
}

public static class Crypt
{
    private const string password = "password";
    private readonly static byte[] salt = Encoding.ASCII.GetBytes(password.Length.ToString());
    public static string FixedEncryptor(string content)
    {
        var cipher = new RijndaelManaged();
        var plain = Encoding.Unicode.GetBytes(content);
        var key = new PasswordDeriveBytes(password, salt);
        using (var encrypt = cipher.CreateEncryptor(key.GetBytes(32), key.GetBytes(16)))
        using (var stream = new MemoryStream())
        using (var crypto = new CryptoStream(stream, encrypt, CryptoStreamMode.Write))
        {
            crypto.Write(plain, 0, plain.Length);
            crypto.FlushFinalBlock();
            return Convert.ToBase64String(stream.ToArray());
        }
    }

    public static string Encryptor(string content)
    {
        var cipher = new RijndaelManaged();
        var plain = Encoding.Unicode.GetBytes(content);
        var key = new PasswordDeriveBytes("password", Encoding.ASCII.GetBytes("password"));
        using (var encrypt = cipher.CreateEncryptor(key.GetBytes(32), key.GetBytes(16)))
        using (var stream = new MemoryStream())
        using (var crypto = new CryptoStream(stream, encrypt, CryptoStreamMode.Write))
        {
            crypto.Write(plain, 0, plain.Length);
            crypto.FlushFinalBlock();
            return Convert.ToBase64String(stream.ToArray());
        }
    }

    public static string FixedDecryptor(string content)
    {
        var cipher = new RijndaelManaged();
        var encrypted = Convert.FromBase64String(content);
        var key = new PasswordDeriveBytes(password, salt);
        using (var decryptor = cipher.CreateDecryptor(key.GetBytes(32), key.GetBytes(16)))
        using (var stream = new MemoryStream(encrypted))
        using (var crypto = new CryptoStream(stream, decryptor, CryptoStreamMode.Read))
        {
            byte[] plain = new byte[encrypted.Length];
            int decrypted = crypto.Read(plain, 0, plain.Length);
            string data = Encoding.Unicode.GetString(plain, 0, decrypted);
            return data;
        }
    }

    public static string Decryptor(string content)
    {
        var cipher = new RijndaelManaged();
        var encrypted = Convert.FromBase64String(content);
        var key = new PasswordDeriveBytes("password", Encoding.ASCII.GetBytes("password"));
        using (var decryptor = cipher.CreateDecryptor(key.GetBytes(32), key.GetBytes(16)))
        using (var stream = new MemoryStream(encrypted))
        using (var crypto = new CryptoStream(stream, decryptor, CryptoStreamMode.Read))
        {
            byte[] plain = new byte[encrypted.Length];
            int decrypted = crypto.Read(plain, 0, plain.Length);
            string data = Encoding.Unicode.GetString(plain, 0, decrypted);
            return data;
        }
    }
}

Fiddel的代码。

但是，这仍然不是“正确”的做事方式。见Sine Nomen's答案

Answer 2

首先，生成盐的方法根本不安全；其次，PasswordDerivedBytes 已弃用，您应该查看它的继任者 Rfc2898DeriveBytes。

尝试以下类似的方法 - 请注意，这需要一些 using 语句：System、System.IO、System.Security.Cryptography 和 System.Text。

只需使用Encrypt(PlainText, Password) 加密数据并使用Decrypt(EncryptedData, Password) 再次解密。 salt 作为前 16 个字节滚动到加密数据中，并且对于每一轮加密/解密都是完全随机的。

这段代码是我自己的开源密码管理器的一部分。

/*
 * Encryption/Decryption, based on AES256 and PBKDF2
 */
public string Encrypt (string plainText, string passPhrase, bool fast_encrypt = false)
{
    string result;
    using (Rijndael algR = Rijndael.Create ()) {
        RNGCryptoServiceProvider rngC = new RNGCryptoServiceProvider ();
        byte[] iv = new byte[16];
        rngC.GetBytes (iv);
        Rfc2898DeriveBytes derived = new Rfc2898DeriveBytes (passPhrase, iv, fast_encrypt ? 10 : 3000);
        algR.KeySize = 256;
        algR.BlockSize = 128;
        algR.Key = derived.GetBytes (32);
        algR.IV = iv;
        using (MemoryStream memoryStream = new MemoryStream ()) {
            memoryStream.Write (iv, 0, 16);
            using (CryptoStream cryptoStreamEncrypt = new CryptoStream (memoryStream, algR.CreateEncryptor (algR.Key, algR.IV), CryptoStreamMode.Write)) {
                using (StreamWriter streamWriterEncrypt = new StreamWriter (cryptoStreamEncrypt)) {
                    streamWriterEncrypt.Write (plainText);
                }
            }

            result = Convert.ToBase64String (memoryStream.ToArray ());
        }
    }

    return result;
}

public string Decrypt (string cipherText, string passPhrase, bool fast_decrypt = false)
{
    string result;
    using (Rijndael algR = Rijndael.Create ()) {
        using (MemoryStream memoryStream = new MemoryStream (Convert.FromBase64String (cipherText))) {
            byte[] iv = new byte[16];
            memoryStream.Read (iv, 0, 16);
            Rfc2898DeriveBytes derived = new Rfc2898DeriveBytes (passPhrase, iv, fast_decrypt ? 10 : 3000);
            algR.KeySize = 256;
            algR.BlockSize = 128;
            algR.Key = derived.GetBytes (32);
            algR.IV = iv;
            using (CryptoStream cryptoStreamDecrypt = new CryptoStream (memoryStream, algR.CreateDecryptor (algR.Key, algR.IV), CryptoStreamMode.Read)) {
                using (StreamReader streamReaderDecrypt = new StreamReader (cryptoStreamDecrypt)) {
                    result = streamReaderDecrypt.ReadToEnd ();
                }
            }
        }
    }

    return result;
}