David O'Brien writes: > On Thu, Sep 13, 2012 at 08:00:19PM +0100, Mark Murray wrote: > > I'm in favour of doing something > > to "dribble" the startup suff in, while limiting its length to (say) > > 1-2 K. Compressing the gathered stuff is a good idea, and inserting > > that *first* with a delay following would be ideal; 1 second would be > > sufficient, 2 safer if the machine very busy. After that "chunking" the > > cached stuff and easing it in slowly would be a Good Thing(tm). > > Mark, > Can you add more about your reasoning why the low-grade entropy should be > input before the high-quality cached entropy?
Sure! I'm presuming that there is sufficient delay after the initial low-grade stuff (compressed, so dense) for it _all_ to be used. This means that at least the first bits of whatever follows also gets used properly. The low-grade stuff is the "best bet" for creating some form of difference between 2 otherwise identical machines, albeit small. This shortish delay also gives the TSC register a bit more time to provide further uncertainty for the later entropy reinsertion/harvesting. The high-grade then does the heavy-lifing, presuming that it exists, which after a dodgy start-up/restart, may not be the case. However, even a small piece of /dev/zero will give SOME entropy due to TSC uncertainty here, so further gathering has a better head start. (There is further help for the super-paranoid; resetting the "seeded" bit (sysctl) will cause /dev/random reads to block until the next reseed. This may be (ab)used to really keep the device safe by repeated clearing followed by writes of cached entropy.) M -- Mark R V Murray Cert APS(Open) Dip Phys(Open) BSc Open(Open) BSc(Hons)(Open) Pi: 132511160 _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-rc To unsubscribe, send any mail to "[email protected]"
