Explain how encryption secure passwords and write a program using either java or python of a hash function that can be used for passwords and give illustration to show how a hash function in cryptography works.

public class Main 
{
    public static void main(String[] args) 
    {
        String passwordToHash = "password";
        String generatedPassword = null;
        try {
            // Create MessageDigest instance for MD5
            MessageDigest md = MessageDigest.getInstance("MD5");
            //Add password bytes to digest
            md.update(passwordToHash.getBytes());
            //Get the hash's bytes 
            byte[] bytes = md.digest();
            //This bytes[] has bytes in decimal format;
            //Convert it to hexadecimal format
            StringBuilder sb = new StringBuilder();
            for(int i=0; i< bytes.length ;i++)
            {
                sb.append(Integer.toString((bytes[i] & 0xff) + 0x100, 16).substring(1));
            }
            //Get complete hashed password in hex format
            generatedPassword = sb.toString();
        } 
        catch (NoSuchAlgorithmException e) 
        {
            e.printStackTrace();
        }
        System.out.println(generatedPassword);
    }
}