access_controller

  def attempt_login
  	authorized_user = User.authenticate(params[:username], params[:hashed_password])
  	if authorized_user
            redirect_to(:action => 'index')
        else
            redirect_to(:action => 'login')
  	end 	
  end

user model

def self.authenticate(username="",password="")
	user = User.find_by_username(username)
	if user && user.hashed_password == password
		return user
	else
		return false
	end
end