如何使用明文字符串和已知的盐生成md5哈希

下面给出的函数为给定的纯文本值生成一个散列，并返回一个base64编码的结果。在计算哈希之前，生成一个随机的salt并将其附加到纯文本中。此盐存储在哈希值的末尾，因此可以稍后用于哈希验证。

要散列的明文值。该函数不检查该参数是否为空。

哈希算法名称。取值为:MD5、SHA1、SHA256、SHA384、SHA512(其他值将使用MD5哈希算法)。

不区分大小写。

在你的例子中设置hashgalgorithm为"MD5"

盐字节。该参数可以为空，否则将生成一个随机的盐值。

格式为base64编码字符串的哈希值。

public static string ComputeHash(string   plainText,
                                 string   hashAlgorithm,
                                 byte[]   saltBytes)
{
    // If salt is not specified, generate it on the fly.
    if (saltBytes == null)
    {
        // Define min and max salt sizes.
        int minSaltSize = 4;
        int maxSaltSize = 8;
        // Generate a random number for the size of the salt.
        Random  random = new Random();
        int saltSize = random.Next(minSaltSize, maxSaltSize);
        // Allocate a byte array, which will hold the salt.
        saltBytes = new byte[saltSize];
        // Initialize a random number generator.
        RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
        // Fill the salt with cryptographically strong byte values.
        rng.GetNonZeroBytes(saltBytes); 
    }
    // 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;
}