On Fri, Jul 13, 2018 at 03:27:14PM -0600, Warren Young wrote: > On Jul 13, 2018, at 3:13 PM, Warren Young <war...@etr-usa.com> wrote: > > > > Now paste in an equivalent number of ‘a’ characters, and you get 0 bits of > > entropy. Strictly speaking, you get 1 bit of entropy for the whole > > message, but it shows 0 because the calculator is rounding the result off > > to 3 significant figures. > > Hmmm…we also need something like a run-length prefix to reconstruct the > message, so this calculator is undershooting slightly. > > For example, 100 a’s requires a 7-bit run-length plus zero bits for our > only code point, so we should get 0.07 bpc, within this calculator’s > apparent precision even without dealing with roundoff errors.
You need more than zero bits to encode the original a though. Frankly, this seems like a bit of pseudo-math to me. The very definition of entropy depends on the context. So a question of "how much entropy does this string have" is seriously underdefined. If you can take the output of any modern CPRNG as hex and don't get 4bpc, the entropy estimator is broken. Joeg _______________________________________________ fossil-users mailing list fossil-users@lists.fossil-scm.org http://lists.fossil-scm.org:8080/cgi-bin/mailman/listinfo/fossil-users
