Casino bosses, take note: Physicists have described a way to guarantee complete randomness in a flow of information, such as the numbers generated by a roulette wheel. The work could allow a person to transform a stream of not-quite-random information into a totally random one. The scientists describe the finding online in Nature Physics.

True randomness — in which a coin flip has a 50 percent chance of coming up heads — is hugely important in fields such as cryptography. Patterns could be detected in a code based on less than random numbers, allowing it to be broken. And if a casino’s random number generators aren’t absolutely random, a gambler might be able to exploit that weakness.