On Wed, Sep 19, 2012 at 7:30 PM, Jonathan Anderson <[email protected]> wrote: > On Tuesday, 18 September 2012 at 22:14, Pawel Jakub Dawidek wrote: >> [=85] we have more >> than 19 bits of entropy from this one call, but I reduced if to four >> bits only, because there are devices that are much faster to attach. >> > > Another reason for doing the above characterization is that, if a particu= lar device_attach() really does provide 12 bits of uncertainty, it's a sham= e to drop eight of them on the floor. Estimating at 4 bits does not drop any entropy on the floor, it just means that if you are going to unblock the PRNG once a certain amount of entropy is present, then this input counts for 4 bits against that certain amount. The amount of entropy harvested is unchanged. The reason to work out how much entropy there is is to: a) Unblock as early as possible b) Not unblock too early Erring on the side of underestimation is wise here. _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-security To unsubscribe, send any mail to "[email protected]"