On Wed, Nov 14, 2018 at 08:22:42PM +1300, Thomas Munro wrote: > On Wed, Nov 14, 2018 at 6:34 PM Noah Misch <n...@leadboat.com> wrote: > > On Wed, Nov 14, 2018 at 05:50:26PM +1300, Thomas Munro wrote: > > > On Wed, Nov 14, 2018 at 3:24 PM Noah Misch <n...@leadboat.com> wrote: > > > > What counts is the ease of predicting a complete seed. HEAD's > > > > algorithm has > > > > ~13 trivially-predictable bits, and the algorithm that stood in > > > > BackendRun() > > > > from 98c5065 until 197e4af had no such bits. You're right that the > > > > other 19 > > > > bits are harder to predict than any given 19 bits under the old > > > > algorithm, but > > > > the complete seed remains more predictable than it was before 197e4af. > > > > > > However we mix them, given that the source code is well known, isn't > > > an attacker's job really to predict the time and pid, two not > > > especially well guarded secrets? > > > > True. Better to frame the issue as uniform distribution of seed, not > > unpredictability of seed selection. > > What do you think about the attached?
You mentioned that you rewrote the algorithm because the new function had a TimestampTz. But the BackendRun() code, which it replaced, also had a TimestampTz. You can reuse the exact algorithm. Is there a reason to change?
