c# - 设置额外的哈希算法

Question

我是 C# 的新手，我正在查看我的前任生成的代码。这是代码:

public static string ComputeHash(string plainText,
                                     string hashAlgorithm, byte[] saltBytes)
    {
        if (saltBytes == null)
            saltBytes = CreateSalt(8);

        // Convert plain text into a byte array.
        byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);

        // Allocate array, which will hold plain text and salt.
        byte[] plainTextWithSaltBytes =
                new byte[plainTextBytes.Length + saltBytes.Length];

        // Copy plain text bytes into resulting array.
        for (int i = 0; i < plainTextBytes.Length; i++)
            plainTextWithSaltBytes[i] = plainTextBytes[i];

        // Append salt bytes to the resulting array.
        for (int i = 0; i < saltBytes.Length; i++)
            plainTextWithSaltBytes[plainTextBytes.Length + i] = saltBytes[i];

        // Because we support multiple hashing algorithms, we must define
        // hash object as a common (abstract) base class. We will specify the
        // actual hashing algorithm class later during object creation.
        HashAlgorithm hash;

        // Make sure hashing algorithm name is specified.
        if (hashAlgorithm == null)
            hashAlgorithm = "";

        // Initialize appropriate hashing algorithm class.
        switch (hashAlgorithm.ToUpper())
        {
            case "SHA1":
                hash = new SHA1Managed();
                break;

            case "SHA256":
                hash = new SHA256Managed();
                break;

            case "SHA384":
                hash = new SHA384Managed();
                break;

            case "SHA512":
                hash = new SHA512Managed();
                break;

            default:
                hash = new MD5CryptoServiceProvider();
                break;
        }

        // Compute hash value of our plain text with appended salt.
        byte[] hashBytes = hash.ComputeHash(plainTextWithSaltBytes);

        // Create array which will hold hash and original salt bytes.
        byte[] hashWithSaltBytes = new byte[hashBytes.Length +
                                            saltBytes.Length];

        // Copy hash bytes into resulting array.
        for (int i = 0; i < hashBytes.Length; i++)
            hashWithSaltBytes[i] = hashBytes[i];

        // Append salt bytes to the result.
        for (int i = 0; i < saltBytes.Length; i++)
            hashWithSaltBytes[hashBytes.Length + i] = saltBytes[i];

        // Convert result into a base64-encoded string.
        string hashValue = Convert.ToBase64String(hashWithSaltBytes);

        // Return the result.
        return hashValue;
    }

    public static bool VerifyHash(string plainText,
                                  string hashAlgorithm,
                                  string hashValue)
    {
        // Convert base64-encoded hash value into a byte array.
        byte[] hashWithSaltBytes = Convert.FromBase64String(hashValue);

        // We must know size of hash (without salt).
        int hashSizeInBits, hashSizeInBytes;

        // Make sure that hashing algorithm name is specified.
        if (hashAlgorithm == null)
            hashAlgorithm = "";

        // Size of hash is based on the specified algorithm.
        switch (hashAlgorithm.ToUpper())
        {
            case "SHA1":
                hashSizeInBits = 160;
                break;

            case "SHA256":
                hashSizeInBits = 256;
                break;

            case "SHA384":
                hashSizeInBits = 384;
                break;

            case "SHA512":
                hashSizeInBits = 512;
                break;

            default: // Must be MD5
                hashSizeInBits = 128;
                break;
        }

        // Convert size of hash from bits to bytes.
        hashSizeInBytes = hashSizeInBits / 8;

        // Make sure that the specified hash value is long enough.
        if (hashWithSaltBytes.Length < hashSizeInBytes)
            return false;

        // Allocate array to hold original salt bytes retrieved from hash.
        byte[] saltBytes = new byte[hashWithSaltBytes.Length -
                                    hashSizeInBytes];

        // Copy salt from the end of the hash to the new array.
        for (int i = 0; i < saltBytes.Length; i++)
            saltBytes[i] = hashWithSaltBytes[hashSizeInBytes + i];

        // Compute a new hash string.
        string expectedHashString =
                    ComputeHash(plainText, hashAlgorithm, saltBytes);

        // If the computed hash matches the specified hash,
        // the plain text value must be correct.
        return (hashValue == expectedHashString);
    }

该公司已升级其安全标准，并要求使用 SHA-1、3DES(三重 DES)或 AES MAC 等安全散列算法。我不知道在哪里包括它们。有人可以帮忙吗？

Answer 1

The company has upgraded their security standards and requires secure hashing algorithms such as SHA-1, 3DES (triple DES) or AES MAC.

首先，你已经有了SHA-1，这个散列算法虽然比SHA-256/512稍微弱一点，但还是很不错的。坚持使用 SHA-512 will keep you very safe ，除非您要与愿意花 10 年时间使用 super 计算机破解您的信息的恶棍打交道。

至于其他两个算法，3DES是对称密码，因此不适合散列，而 MACs 使用散列算法创建，例如 SHA-2(不同之处在于您在消息中散列一个“ key ”(类似于“固定盐”)以确保其真实性。AES 是也是对称密码，因此也不适合散列。

让你们公司的人查一下this page并满足于这些哈希函数之一(换句话说:不要改变任何东西)。如果您没有密码学方面的经验，那么无论您选择何种哈希算法，您都可能会使系统变得不安全。