Jinkster your right about dithering, i believe it was a method used by the US military to alternate the times in the atomic clocks in the gps satellites so that your position would be less precise when you are using a "civil" gps-system. The military did have the special code to reveal what the real timing was so they could be more precize, and maintain the advantage on users of the civil-system.
And ETOPS requirements have to do with reliability and maintenance of the engines of the aircraft, they have to be proven to be within certain limits (i'm sure you can find them at google)