Subject: Re: Hardware random number generator
From: (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.