Talk:Main Page/Archive 1

This page serves as an archive for clearly Handled topics, as Talk:Main Page is getting a little cluttered.

md5 Collisions?

What about collisions in the md5 algorithm?

What about them? In theory, two dates/stock market prices might end up with the same meetup point. Unlikely, and probably not a terribly big deal? Zigdon 07:39, 21 May 2008 (UTC)

There are situations where cryptographic collisions are a problem, but this isn't one of them. md5 is just being used as a pseudorandom number generator here, and it has a very small-entropy seed (someone call Debian!). So its cryptographic strenth isn't particularly relevant. --Xkcd 07:43, 21 May 2008 (UTC)xkcd

OMG geohashing predicts future dow prices!

http://irc.peeron.com/xkcd/map/data/2009/05/27 --Ryan the leach 12:33, 21 May 2008 (UTC)

heh yeh i saw that one too... this is deep magic SinJax

Yeah, I totally wasn't testing stuff, <_< Zigdon 14:54, 21 May 2008 (UTC)

Wow, now you only need to break MD5 to get rich! 81.167.17.12 12:40, 21 May 2008 (UTC)

could be future meetup? --Ryan the leach 12:33, 21 May 2008 (UTC)

Fairly inconsistent if so, what if the dow is different. WHAT THEN?!?

It won't ;) --DarkRat

well the tool wont say its different :P --Ryan the leach 12:33, 21 May 2008 (UTC)

geohash.org

There's already a thing called "geohash" which is a way to represent coordinates with arbitrary precision in a computer and query-friendly format. It's at http://geohash.org/ and it was designed and implemented by Gustavo Niemeyer.

I don't see how that's relevant. We are talking about geohashing. It's a different word.

To decimal

...now, i'm likely just too thick to get it, but how does one convert back from the half md5 hash to decimals?

It goes like this... each digit is below zero but not 10^-n but 16^-n....so the first hex digit is 16^-1, the next is 16^-2 and so on. And it goes from left to right so in the hex number "8d" you get:

f = (8 * 16^-1) + (13 * 16^-2) = 0.5507

i think anyway :) - SinJax

Or, interpret the bytes from md5 as two big-endian 64-bit integers, and divide both by 2^64.

Chicago area

In the northern Chicago suburbs, the vast majority of nearby GPS areas according to the implementation are dangerous pools of dihydrogen monoxide. Is there some workaround?

Chicago area residents could just use which ever of the four locations makes the most sense. (See the Chicago page.)

Believe Adelaide in South Australia Has a similair problem but nowhere quite as severe.

dihydrogen monoxide should be avoided at all costs, if you're careful, you could go to the nearest point at the shore of the dihidrogen monoxide pool, but be sure to not ingest any.

While i'm probably the only Milwaukeean who is going to be running around and playing, my region is about 80% Lake Michigan. No good.

My region is a similar amount English Channel and Solent. I guess this just makes the occasional on-land meetup more special - perversely, I think it might actually *keep* people's attention longer. 81.187.153.189 18:45, 21 May 2008 (UTC)

xkcd.com/geohashing Problems?

Hey - I can't get to [1], and none of the graticules' maps are working - is this just me, or the rest of the world, too?

Yes, irc.peeron.com is currently down (as of 20080523 11pm PDT), I know, I'm trying to get hold of someone who can do something about it. Zigdon 07:29, 23 May 2008 (UTC)

Why is the the xkcd.com/geohashing redirecting to irc.peeron.com anyway, shouldn't it be moved to xkcd? I think too many active graticulees are melting the server. --Opspin 08:07, 23 May 2008 (UTC)

it's working again!

Difference between the comic and the generator

Zigdon, xkcd:

The hash in the comic for 2005-05-26-10458.68 starts with db9318........

Here's debugging info for the map page's calculation of http://irc.peeron.com/xkcd/map/:

Graticule: (37, -123) - (38, -122)
Market open on 2005-05-26 = 10458.68
MD5(2005-05-26-10458.68 ): 357e5cac889681628fdd754c1a235919
Split: 357e5cac88968162, 8fdd754c1a235919
offset = 0.20895938122029104, 0.5619729338451526
37.20895938122029 -122.56197293384515

On my machine: $ md5 -s "2005-05-26-10458.68"
MD5 ("2005-05-26-10458.68") = db9318c2259923d08b672cb305440f97

Any idea what's going on here? Is that an extra space on the end there, Zig?
--FunkyTuba

   I've found a bunch of opening values at http://irc.peeron.com/xkcd/map/data/
   with carriage returns on the end, which I dont think were being stripped out before
   hashing. The website went down before I could fully confirm though.
   --ZorMonkey 11:49, 23 May 2008 (UTC)

That was indeed the case, fixed now. Zigdon 14:07, 23 May 2008 (UTC)