[Cryptography] Caches considered harmful

[Jerry Leichter]

> Autopilots in particular, if too predictable, are open to attacks
> against herds of cars resulting in massive traffic jams etc, which are
> non-issues if they are individually somewhat probabilistic....
It depends on what kinds of attacks you're talking about.

If you're talking about a mass attack that knows nothing about the individual cars, but, e.g., you set up a situation where they will all make the same decision putting them all on the same bypass - which is then promptly overloaded - then you don't need *probabilistic* algorithms:  You need *variations within the algorithms*.  So each car might find the best 5 alternatives (all perhaps reaching the same decisions), but then choose one of them based on the car's serial number.  Perfectly predictable, given the additional information.

Of course, if the attack you're talking about assumes the attacker knows all the serial numbers and can tailor the attack to herd all the cars together, or something of that sort, you're in a different domain.

Note that having variation among instances is basic to biological systems.  Since the species as a whole doesn't "know" the exact environments in which its members will need to survive, fielding a bunch of variations, each optimized for a slightly different environment, is the best approach.  This is particularly obvious in various "settings" that influence reactions to disease organisms.

                                                        -- Jerry