I have wondered about this quite a lot of times and I'm trying to attempt this problem with my ... A mobile recharge card have a hidden pin no which can be used to fill some amount. ... If you find an answer or an algorithm to generate those numbers... let us know... those algorithms are the base of security to prevent fraud ...With a 12 digit code, we have 900 billion combinations with a non-zero first digit. Way above our annual needs. These could serve us for about
