India, July 21 -- Every UPI payment, OTP and encrypted message rests on numbers nobody can predict - yet India imports its randomness in sealed black boxes it has never checked

Your phone buzzes. A six-digit code appears - a one-time password, or OTP. You type it in, the payment goes through, and you forget the number forever. It lived for less than a minute. And in that minute, it had only one job: to be impossible for anyone on Earth to guess. This little ritual repeats in India about nine thousand times every second. In June alone, the Unified Payments Interface (UPI) handled 22.72 billion payments - roughly 757 million a day. Every one of them begins with secret numbers that must be unpredictable. So does every Aadhaar check, every p...