Question

I have developed a sample app, which uses Facebook features, and it is working fine on my device(Samsung Galaxy S). For including Facebook features, i created a dev account(as required) and generated a key hash which i entered in FB dev account.My doubt is(I know it may be very silly to ask this), why do we need to enter this key hash in FB website when we ourselves will be signing the .apk and releasing it in market? Of what use will this key hash be to FB or the device that is downloading my app?

Answer 1

It’s just another security measure from facebook since it will allow your app to retrieve personal information. Sic, from http://www.facebook.com/developers :

A security key used for a more
seamless login experience (e.g.,
snY1_9SPiOfe_xK2D-RT2ASFl5k).

This is specially important in mobile devices, since you may use it even without logging in: (SIC) From http://developers.facebook.com/docs/guides/mobile/#android_key_hash :

Single-Sign-On (SSO)

As with the iOS SDK, one of the most
compelling features of the Android SDK
is Single-Sign-On (SSO). SSO lets
users sign into your app using their
Facebook identity. If they are already
signed into the Facebook Android app
on their device they do not have to
even type a username and password.
Further, because they are signing to
your app with their Facebook identity,
you will have access to their profile
information and social graph.