Cracking the Scratch Lottery Code

Feb. 4, 2011— -- Mohan Srivastava, a geological statistician living in Toronto, was working in his office in June 2003, waiting for some files to download onto his computer, when he discovered a couple of old lottery tickets buried under some paper on his desk. The tickets were cheap scratchers—a gag gift from his squash partner—and Srivastava found himself wondering if any of them were winners. He fished a coin out of a drawer and began scratching off the latex coating. "The first was a loser, and I felt pretty smug," Srivastava says. "I thought, 'This is exactly why I never play these dumb games.'"

The second ticket was a tic-tac-toe game. Its design was straightforward: On the right were eight tic-tac-toe boards, dense with different numbers. On the left was a box headlined "Your Numbers," covered with a scratchable latex coating. The goal was to scrape off the latex and compare the numbers under it to the digits on the boards. If three of "Your Numbers" appeared on a board in a straight line, you'd won. Srivastava matched up each of his numbers with the digits on the boards, and much to his surprise, the ticket had a tic-tac-toe. Srivastava had won $3. "This is the smallest amount you can win, but I can't tell you how excited it made me," he says. "I felt like the king of the world."

Delighted, he decided to take a lunchtime walk to the gas station to cash in his ticket. "On my way, I start looking at the tic-tac-toe game, and I begin to wonder how they make these things," Srivastava says. "The tickets are clearly mass-produced, which means there must be some computer program that lays down the numbers. Of course, it would be really nice if the computer could just spit out random digits. But that's not possible, since the lottery corporation needs to control the number of winning tickets. The game can't be truly random. Instead, it has to generate the illusion of randomness while actually being carefully determined."

Srivastava speaks quietly, with a slight stammer. He has a neatly trimmed beard and a messy office. When he talks about a subject he's interested in—and he's interested in many things, from military encryption to freshwater fossils—his words start to run into each other.

As a trained statistician with degrees from MIT and Stanford University, Srivastava was intrigued by the technical problem posed by the lottery ticket. In fact, it reminded him a lot of his day job, which involves consulting for mining and oil companies. A typical assignment for Srivastava goes like this: A mining company has multiple samples from a potential gold mine. Each sample gives a different estimate of the amount of mineral underground. "My job is to make sense of those results," he says. "The numbers might seem random, as if the gold has just been scattered, but they're actually not random at all. There are fundamental geologic forces that created those numbers. If I know the forces, I can decipher the samples. I can figure out how much gold is underground."