使用 Salt/IV 创建/解密密码

Question

我被要求在一个涉及 Windows 8 加密的项目中执行一项任务。

场景是这样的：

我byte[]从服务器得到一个，前 16 个字节是IV，接下来的 128 个是Salt，其余的是文件本身。

然后用户提供一个密码，并使用该密码和盐，我应该创建一个 PKCS5 密钥，迭代 40 次，密钥长度应为 32 字节。

现在我已经拆分了byte[]我需要的 3 个，但我不知道其余的在 Windows C# 中是如何完成的。

Answer 1

我在加密/解密方面做了一些工作，但让我给你我用于 AES 256 位加密的资源。希望这能让您了解如何将其切换到 PKCS5，但我很确定其他所有内容都是相同的。这有点冗长，但如果这适用于您的情况，请告诉我。我很好奇 PKCS5 而不是 AES256 会有多大不同。

编辑：因为他们发布的代码在迭代中不清楚，所以迭代由var key = Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);使用 1000 次迭代的行控制。

http://www.codeproject.com/Articles/769741/Csharp-AES-bits-Encryption-Library-with-Salt

核心加密代码

using System.Security.Cryptography;
using System.IO;

加密

public byte[] AES_Encrypt(byte[] bytesToBeEncrypted, byte[] passwordBytes)
{
    byte[] encryptedBytes = null;

    // Set your salt here, change it to meet your flavor:
    // The salt bytes must be at least 8 bytes.
    byte[] saltBytes = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 };

    using (MemoryStream ms = new MemoryStream())
    {
        using (RijndaelManaged AES = new RijndaelManaged())
        {
            AES.KeySize = 256;
            AES.BlockSize = 128;

            var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
            AES.Key = key.GetBytes(AES.KeySize / 8);
            AES.IV = key.GetBytes(AES.BlockSize / 8);

            AES.Mode = CipherMode.CBC;

            using (var cs = new CryptoStream(ms, AES.CreateEncryptor(), CryptoStreamMode.Write))
            {
                cs.Write(bytesToBeEncrypted, 0, bytesToBeEncrypted.Length);
                cs.Close();
            }
            encryptedBytes = ms.ToArray();
        }
    }

    return encryptedBytes;
}

解密

public byte[] AES_Decrypt(byte[] bytesToBeDecrypted, byte[] passwordBytes)
{
    byte[] decryptedBytes = null;

    // Set your salt here, change it to meet your flavor:
    // The salt bytes must be at least 8 bytes.
    byte[] saltBytes = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 };

    using (MemoryStream ms = new MemoryStream())
    {
        using (RijndaelManaged AES = new RijndaelManaged())
        {
            AES.KeySize = 256;
            AES.BlockSize = 128;

            var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
            AES.Key = key.GetBytes(AES.KeySize / 8);
            AES.IV = key.GetBytes(AES.BlockSize / 8);

            AES.Mode = CipherMode.CBC;

            using (var cs = new CryptoStream(ms, AES.CreateDecryptor(), CryptoStreamMode.Write))
            {
                cs.Write(bytesToBeDecrypted, 0, bytesToBeDecrypted.Length);
                cs.Close();
            }
            decryptedBytes = ms.ToArray();
        }
    }

    return decryptedBytes;
}

使用 Salt 获得随机加密结果

如果我们对同一个上下文（即“Hello World”的字符串）加密10次，加密的结果是一样的。如果我们希望每次加密的结果都不同怎么办？

我所做的是在加密前在原始字节前面附加一个随机盐字节，并在解密后将其删除。

在加密字符串之前附加随机盐的示例

public string Encrypt(string text, string pwd)
{
    byte[] originalBytes = Encoding.UTF8.GetBytes(text);
    byte[] encryptedBytes = null;
    byte[] passwordBytes = Encoding.UTF8.GetBytes(pwd);

    // Hash the password with SHA256
    passwordBytes = SHA256.Create().ComputeHash(passwordBytes);

    // Generating salt bytes
    byte[] saltBytes = GetRandomBytes();

    // Appending salt bytes to original bytes
    byte[] bytesToBeEncrypted = new byte[saltBytes.Length + originalBytes.Length];
    for (int i = 0; i < saltBytes.Length; i++)
    {
        bytesToBeEncrypted[i] = saltBytes[i];
    }
    for (int i = 0; i < originalBytes.Length; i++)
    {
        bytesToBeEncrypted[i + saltBytes.Length] = originalBytes[i];
    }

    encryptedBytes = AES_Encrypt(bytesToBeEncrypted, passwordBytes);

    return Convert.ToBase64String(encryptedBytes);
}

解密后去盐示例

public string Decrypt(string decryptedText, string pwd)
{
    byte[] bytesToBeDecrypted = Convert.FromBase64String(decryptedText);
    byte[] passwordBytes = Encoding.UTF8.GetBytes(pwd);

    // Hash the password with SHA256
    passwordBytes = SHA256.Create().ComputeHash(passwordBytes);

    byte[] decryptedBytes = AES_Decrypt(bytesToBeDecrypted, passwordBytes);

    // Getting the size of salt
    int _saltSize = 4;

    // Removing salt bytes, retrieving original bytes
    byte[] originalBytes = new byte[decryptedBytes.Length - _saltSize];
    for (int i = _saltSize; i < decryptedBytes.Length; i++)
    {
        originalBytes[i - _saltSize] = decryptedBytes[i];
    }

    return Encoding.UTF8.GetString(originalBytes);
}

获取随机字节的代码

public byte[] GetRandomBytes()
{
    int _saltSize = 4;
    byte[] ba = new byte[_saltSize];
    RNGCryptoServiceProvider.Create().GetBytes(ba);
    return ba;
}