• 12/05/2008
•   ASP.NET, WinForms

MD5 hashing can be used as a quick and easy way to check if a string was changed or not. I created a class to let me get the hash or verify it with 1 line of code.

    
public class MD5Strings
    {
        // Hash an input string and return the hash as
        // a 32 character hexadecimal string.
        public static string getMd5Hash(string input)
        {
            // Create a new instance of the MD5CryptoServiceProvider object.
            MD5 md5Hasher = MD5.Create();

            // Convert the input string to a byte array and compute the hash.
            byte[] data = md5Hasher.ComputeHash(
                 Encoding.Default.GetBytes(input));

            // Create a new Stringbuilder to collect the bytes
            // and create a string.
            StringBuilder sBuilder = new StringBuilder();

            // Loop through each byte of the hashed data
            // and format each one as a hexadecimal string.
            for (int i = 0; i < data.Length; i++)
            {
                sBuilder.Append(data[i].ToString("x2"));
            }

            return sBuilder.ToString();  // Return the hexadecimal string.
        }

        // Verify a hash against a string.
        public static bool verifyMd5Hash(string input, string hash)
        {
            string hashOfInput = getMd5Hash(input);  // Hash the input.

            //Create a StringComparer an comare the hashes.
            StringComparer comparer = StringComparer.OrdinalIgnoreCase;

            if (0 == comparer.Compare(hashOfInput, hash))
            {
                return true;
            }
            else
            {
                return false;
            }
        }
    }

Now, to get the hash of a string:

string result;

//return the hash in uppercase to make it a little more presentable
result = MD5Strings.getMd5Hash("Hello, World!").ToUpper();

And to verify a hash:

bool verify = MD5Strings.verifyMd5Hash("Hello, World!",
    "65A8E27D8879283831B664BD8B7F0AD4");