Subject: Re: Hardware random number generator From: firstname.lastname@example.org (Steven Bellovin) In fact, that's more or less the way the AT&T random number generator chip works. However, it only produces one bit of output at a time; there's no shift register. The low-frequency oscillator is used to generate sample times. There's a FIFO to store the generated bits. And there are frills, such as a (simple) statistical test at initialization time. There are a few things to be careful of, such as the ratio between the oscillator frequencies -- if they're too close, you don't get random enough bits. Also, be *very* careful to avoid coupling between the two oscillators. The chip has on-board oscillators, but the data sheet says that you get better results if you don't use them.