access condition ff0780

Hello
I am facing problem regarding authentication of mifare card.
By default the "key A" used for authentication holds data
FFFFFFFFFFFF
i want to change it to something else which can provide me privacy
i read the documentation of the card and also found the detail and understood it.
May be there is problem with my understanding but the technique is not working.

I am not able to change the authentication key.
Plz help me

I am also attaching the document which i consulted regrading the access conditions
presently i am having the data
011100000000000000FF078069FFFFFFFFFFFF01
the underlined area is representing the authentication code