Quickie blurb on using video card retraces as a source of entropy... I've done some brief testing in the last couple of days on using the timing drift between video retrace events as a source of randomness. It seems comparable to truerand() spinners that check the system's timer ticks [which makes me leary of relying on it since it has similar strange attractors when plotted in a noise sphere, but that's another post...]. Assuming one trusts truerand spinners, this method could have some advantages over a 'pure software' method, since the video controller (and other hardware controllers which could be adapted to this) runs in 'parallel' [although it's liable to the samefluctuations in current or memory-access and other interfaces with the main system, or possibly tempest attacks for the paranoid...]. In pseudo-C: int retrace(void) { // test for video retrace #ifdef __MSDOS__ return (port[0x3da] & 8); // Some VGA, maybe EGA cards #else // your OS here #endif } [..] x = 0; while (!retrace()) x++; I've tested it as standalone routines (in Pascal and assembler) as well as a hook to the DOS idle in the background [See note about strange atteactors above]. It also seems to work while in Windows (but not OS/2?!), which is an advantage over using the system's microsecond timer alarm (which Win3 takes over). Comments? (other than "truerand is an oxymoron"....) Rob. --- Send a blank message with the subject "send pgp-key" to <WlkngOwl@unix.asb.com> for a copy of my PGP key.