PS: converting the result of MD5 hashMessage: to hex is a total waste of time. Just ask: - is the first byte zero? - is the second byte zero? - is the third byte less than 16?
On Thu, 13 Dec 2018 at 00:07, Richard O'Keefe <rao...@gmail.com> wrote: > This is the puzzle where you have to find the smallest integer such that > '<some salt>' , (that integer) printString has an MD5 hash beginning with > 5 hexadecimal zeros? > > Brute force is just fine. Calling libnettle's MD5 functions from a C > program, it found the right answer in under 0.2 seconds on a cheap laptop. > If using the MD5 class in Pharo doesn't take a reasonable time, you may > find that (MD5 isPluginAvailable) is false. On my cheap laptop, the > obvious code took 30 seconds to find the right answer, which surely means > that the plugin is *not* available. But there is absolutely no point in > looking for anything faster. > > So, > (0 to: 1000000) findFirst: [:n | |digest| > digest := MD5 hashMessage: 'YOUR SALT GOES HERE' , n printString. > ... bytes begins with 00000 ...] > > Linear search. > Compute string. > Compute its MD5 hash. > Check the result. > > The only time-consuming thing was browsing the MD5 class (and its > superclass HashFunction) to figure out the interface. > > Now it *could* have turned out to be too slow to be useful, in which > case another strategy would have been needed. But it didn't. > (I started with a rather smaller bound to get an idea of how fast it > was, and it was fast enough.) > > > > On Mon, 10 Dec 2018 at 00:30, Roelof Wobben <r.wob...@home.nl> wrote: > >> Helllo, >> >> a question about day4 of 2015 >> is it right that I can only solve this bruteforece >> so begin at for example 1 , encode it, check for 5 zeros if found then I >> have found it otherwise increase the counter and do it again >> https://adventofcode.com/2015/day/4 >> >> Regards, >> >> Roelof >> >>
