At 8:30 12/13/95 -0500, Josh M. Osborne wrote:

In message <199512120056.QAA16055@mage.qualcomm.com>, Peter Monta writes:

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Of course, this works against a remote adversary, but not against one on the same machine who can look at actual CPU consumption (which doesn't increase when the target is blocked).

Maybe this is a good reason to spinwait, rather than sleep, until the timer expires. It would be pretty subtle to distinguish that from "real" computation.

Across a net it should be hard. On the same CPU it may be easy. Some CPUs with hardware branch prediction keep track of how many branches were correctly and incorrectly predected. These registers are not allways protected, and not allways "made virtual" by the OS.

Of course you can spend the time doing exponentiation of random (pseudorandom would probably do) numbers, and when the timer pops, longjump out to return your answer. ----------------------------------------------------------------- Bill Frantz Periwinkle -- Computer Consulting (408)356-8506 16345 Englewood Ave. frantz@netcom.com Los Gatos, CA 95032, USA