How to perform change password functionality?

Rails
1

Dear all,

Iam in process of creation an admin panel, i have used

def sign_in

if request.get?

  flash.now[ :notice ] = 'Please enter your username and password'

elsif request.post? and params[ :admin ]

  session[ :admin_id ]  = nil

  @admin = Admin.authenticate(params[:admin][:email],
                              params[:admin][:password])

  if @admin

    session[ :admin_id ] = @admin.id
    session[ :admin ]    = @admin.name

    redirect_to :action => "list"

  else

    flash.now[ :error ] = 'The username or password entered is

incorrect’

  end

end

end

def add

 if request.post? and params[ :admin ]


  @admin = Admin.new( params[ :admin ])

  @admin.name = params[ :admin ][ :name ]

  @admin.email = params[ :admin ][ :email ]

  admin_password =

Digest::SHA1.hexdigest("–#{Time.now.to_s}–#{@admin.name}–")[0,6]

  @admin.password = Base64.encode64(admin_password)


  if @admin.save

    @admin = Admin.find(@admin.id)

    #calls the sent_order method
    Adminpassword.deliver_sent(@admin)

    # if so...
    redirect_to :action => 'list'

  end

else

  # render an empty admin instance
  @admin = Admin.new

end

end

my add and sign in functions are working well, and while iam using
change password method i was not able to perform the operation.

Could any one suggest on using change password option for my above
controller,
i have tried the method with following code,

def change_password

if request.get?

  # if so ...
  @admin = Admin.new

# was this action invoked by a post request?
elsif request.post?


  admin = session[ :admin]

  admin.update_attributes(:password => params[:new_password])

  #@admin.password = params[ :old_password ]

  #@admin.update_attributes( :new_password )

  if admin.save

       flash[:notice] =  'Password changed successfully'
       redirect_to :controller => 'admin', :action => 'list'

                  end


else

  flash.now[:notice] = 'Please enter the required parameters'

end

end

Thanks in advance

Regards,
Jose martin