custom Authentication

gistfile1.rb

I have this issue, i'm new to rails. This is a custom authentication code, but when i enter a email address contained in my database, i get "Invalid Email/password Combination",
If i enter a valid email address but leave the password field blank, the user is loged in,What am i doing wrong please?

User.rb 

 def has_password?(submitted_password)
    encrypted_password == encrypt(submitted_password)
    end

class << self    
    def authenticate(email, submitted_password)
      user = find_by_email(email)
     return nil  if user.nil?
    return user if user.has_password?(submitted_password)
    end

  
    def authenticate_with_salt(id, cookie_salt)
      user = find_by_id(id)
      (user && user.salt == cookie_salt) ? user : nil
    end
  end  
  
   private
       def encrypt_password
         self.salt = make_salt if new_record?
         self.encrypted_password = encrypt(password)
       end

       def encrypt(string)
         secure_hash("#{salt}--#{string}")
       end

       def make_salt
         secure_hash("#{Time.now.utc}--#{password}")
       end

       def secure_hash(string)
         Digest::SHA2.hexdigest(string)
       end
   end

  SessionController.rb 
  
  def create
    user = User.authenticate(params[:session][:email],
                             params[:session][:password])
    if user.nil?
      flash.now[:error] = "Invalid email/password combination."
      @title = "Sign in"
      render 'new'
    else
      sign_in user
	 redirect_back_or user
    end
  end
  
  sessions/new.html.erb
  ..
  <%= form_for(:session, :url => sessions_path,:class => "expandedform") do |f| %>
  <fieldset class=" round clearfix">
    <legend align="center">Enter Logon Details</legend>
    <div class="row" align="center">
    <%= f.label :email %><br />
    <%= f.text_field :email,:class=>"texttop"%>
  </div>
  <div class="row" align="center">
    <%= f.label :password %><br />
    <%= f.password_field :password,:class =>"texttop"%>
  </div>
  <div class="row" align="center">
    <%= f.submit "Sign in", :class=> "new_project round" %>
  </div>
    <div class="row" align="center">New user? <%= link_to "Sign up now!", signup_path %></div>
    <div class="row" align="center"><%= link_to "Forgot Password!", new_password_reset_path%></div>
      </fieldset>
<% end %>