When dealing with message into an application, and the message that you are receiving or sending is over a not trusted channel you should think about a way to make sure that the message has not been altered. This is why cryptographic hash functions are used.
More on cryptographic hash function you can find here.
Here is a function in C# that can generate for you the hash of a string based on your favorite algorithm.

using System;
using System.Text;
using System.Security.Cryptography;

/// <summary>
/// Hash algorithms
/// </summary>
public enum HashType : int
{
    SHA1,
    SHA256,
    SHA384,
    SHA512,
    MD5,
    RIPEMD160
}

public static class Hash
{
    public static string FromString(string input, HashType hashtype)
    {
        Byte[] clearBytes;
        Byte[] hashedBytes;
        string output = String.Empty;

        switch (hashtype)
        {
            case HashType.RIPEMD160:
                clearBytes = new UTF8Encoding().GetBytes(input);
                RIPEMD160 myRIPEMD160 = RIPEMD160Managed.Create();
                hashedBytes = myRIPEMD160.ComputeHash(clearBytes);
                output = BitConverter.ToString(hashedBytes).Replace("-", "").ToLower();
                break;
            case HashType.MD5:
                clearBytes = new UTF8Encoding().GetBytes(input);
                hashedBytes = ((HashAlgorithm)CryptoConfig.CreateFromName("MD5")).ComputeHash(clearBytes);
                output = BitConverter.ToString(hashedBytes).Replace("-", "").ToLower();
                break;
            case HashType.SHA1:
                clearBytes = Encoding.UTF8.GetBytes(input);
                SHA1CryptoServiceProvider sha1 = new SHA1CryptoServiceProvider();
                sha1.ComputeHash(clearBytes);
                hashedBytes = sha1.Hash;
                sha1.Clear();
                output = BitConverter.ToString(hashedBytes).Replace("-", "").ToLower();
                break;
            case HashType.SHA256:
                clearBytes = Encoding.UTF8.GetBytes(input);
                SHA256 sha256 = new SHA256Managed();
                sha256.ComputeHash(clearBytes);
                hashedBytes = sha256.Hash;
                sha256.Clear();
                output = BitConverter.ToString(hashedBytes).Replace("-", "").ToLower();
                break;
            case HashType.SHA384:
                clearBytes = Encoding.UTF8.GetBytes(input);
                SHA384 sha384 = new SHA384Managed();
                sha384.ComputeHash(clearBytes);
                hashedBytes = sha384.Hash;
                sha384.Clear();
                output = BitConverter.ToString(hashedBytes).Replace("-", "").ToLower();
                break;
            case HashType.SHA512:
                clearBytes = Encoding.UTF8.GetBytes(input);
                SHA512 sha512 = new SHA512Managed();
                sha512.ComputeHash(clearBytes);
                hashedBytes = sha512.Hash;
                sha512.Clear();
                output = BitConverter.ToString(hashedBytes).Replace("-", "").ToLower();
                break;
        }
        return output;
    }
}