4 ms·

How Allies Used Math Against German Tanks

37 points by Luyt 16y ago

bl4k 16y ago
or why to not put autoincrement id's into your webapp routes
- Luyt 16y ago
  ...because others then can find out how many visitors your site gets? Or perhaps nastier things, like guessing id's?
  - jjwiseman 16y ago
    Previously: http://news.ycombinator.com/item?id=670218 http://news.ycombinator.com/item?id=670218, http://news.ycombinator.com/item?id=1818166 http://news.ycombinator.com/item?id=1818166, joshu: http://joshua.schachter.org/2007/01/autoincrement.html http://joshua.schachter.org/2007/01/autoincrement.html (http://news.ycombinator.com/item?id=52429 http://news.ycombinator.com/item?id=52429 ) Foursquare growth in 2009 inferred from autoincrement IDs: http://www.flickr.com/photos/wallofhair/4232092914/ http://www.flickr.com/photos/wallofhair/4232092914/
    - joshu 16y ago
      I have a bunch of similar data on craigslist I should write up someday.
    - gokhan 16y ago
      One from 2006: http://www.guardian.co.uk/world/2006/jul/20/secondworldwar.tvandradio http://www.guardian.co.uk/world/2006/jul/20/secondworldwar.t... "The statisticians believed that the Germans, being Germans, had logically numbered their tanks in the order in which they were produced."
    - gojomo 16y ago
      For some services, your growth may not be proprietary info — you may want to show incrementing IDs off, or make all your artifacts trivially discoverable. But, if you have an internal autoincrement ID that you want to obfuscate, what's the best simple practice, minimizing token expansion?
      - smanek 16y ago
        Just use UUIDs and be done with it. I'll give you a $1 if you ever see a collision ;-)
        gojomo 16y ago
        That's a reasonable baseline suggestion, but I'd prefer any technique to generate more compact public IDs.
        buddydvd 16y ago
        http://www.quora.com/How-do-you-symmetrically-encrypt-32-bit-auto-increment-IDs-to-avoid-using-64-bit-UUIDs-to-conceal-the-size-and-order-of-a-database-table/answers/23925 http://www.quora.com/How-do-you-symmetrically-encrypt-32-bit...
lucasjung 16y ago
When I saw the headline, I my first thought was that the math was something along the lines of: A = number of U.S./allied tanks in each battle D = number of German/axis tanks in each battle A >= 2D
mivok 16y ago
If you like stories like this, there are a number of similar stories (e.g. this one, cracking the enigma code, protecting convoys) in a book called The Pleasures of Counting: http://www.amazon.com/Pleasures-Counting-T-W-K%C3%B6rner/dp/0521568234 http://www.amazon.com/Pleasures-Counting-T-W-K%C3%B6rner/dp/... - it's not all world war 2, but is very interesting and does contain a lot of information on the math used during the war.
RiderOfGiraffes 16y ago
If you care to search you'll find that this story has appeared here on HN several times in the past several months. There has been much discussion, again and again. I'm currently on my mobile and can't easily search for you. EDIT: OK, I've got to a proper computer and here are some search results: http://news.ycombinator.com/item?id=670218 http://news.ycombinator.com/item?id=670218 http://news.ycombinator.com/item?id=1421698 http://news.ycombinator.com/item?id=1421698 http://news.ycombinator.com/item?id=1818166 http://news.ycombinator.com/item?id=1818166 Each of these has substantial discussion, and I'm pretty sure there are more.

37 points by Luyt 16y ago

bl4k 16y ago

or why to not put autoincrement id's into your webapp routes

Luyt 16y ago
...because others then can find out how many visitors your site gets? Or perhaps nastier things, like guessing id's?
- jjwiseman 16y ago
  Previously: http://news.ycombinator.com/item?id=670218 http://news.ycombinator.com/item?id=670218, http://news.ycombinator.com/item?id=1818166 http://news.ycombinator.com/item?id=1818166, joshu: http://joshua.schachter.org/2007/01/autoincrement.html http://joshua.schachter.org/2007/01/autoincrement.html (http://news.ycombinator.com/item?id=52429 http://news.ycombinator.com/item?id=52429 ) Foursquare growth in 2009 inferred from autoincrement IDs: http://www.flickr.com/photos/wallofhair/4232092914/ http://www.flickr.com/photos/wallofhair/4232092914/
  - joshu 16y ago
    I have a bunch of similar data on craigslist I should write up someday.
  - gokhan 16y ago
    One from 2006: http://www.guardian.co.uk/world/2006/jul/20/secondworldwar.tvandradio http://www.guardian.co.uk/world/2006/jul/20/secondworldwar.t... "The statisticians believed that the Germans, being Germans, had logically numbered their tanks in the order in which they were produced."
  - gojomo 16y ago
    For some services, your growth may not be proprietary info — you may want to show incrementing IDs off, or make all your artifacts trivially discoverable. But, if you have an internal autoincrement ID that you want to obfuscate, what's the best simple practice, minimizing token expansion?
    - smanek 16y ago
      Just use UUIDs and be done with it. I'll give you a $1 if you ever see a collision ;-)
      - gojomo 16y ago
        That's a reasonable baseline suggestion, but I'd prefer any technique to generate more compact public IDs.
        buddydvd 16y ago
        http://www.quora.com/How-do-you-symmetrically-encrypt-32-bit-auto-increment-IDs-to-avoid-using-64-bit-UUIDs-to-conceal-the-size-and-order-of-a-database-table/answers/23925 http://www.quora.com/How-do-you-symmetrically-encrypt-32-bit...

lucasjung 16y ago

When I saw the headline, I my first thought was that the math was something along the lines of: A = number of U.S./allied tanks in each battle D = number of German/axis tanks in each battle A >= 2D

mivok 16y ago

If you like stories like this, there are a number of similar stories (e.g. this one, cracking the enigma code, protecting convoys) in a book called The Pleasures of Counting: http://www.amazon.com/Pleasures-Counting-T-W-K%C3%B6rner/dp/0521568234 http://www.amazon.com/Pleasures-Counting-T-W-K%C3%B6rner/dp/... - it's not all world war 2, but is very interesting and does contain a lot of information on the math used during the war.

RiderOfGiraffes 16y ago

If you care to search you'll find that this story has appeared here on HN several times in the past several months. There has been much discussion, again and again. I'm currently on my mobile and can't easily search for you. EDIT: OK, I've got to a proper computer and here are some search results: http://news.ycombinator.com/item?id=670218 http://news.ycombinator.com/item?id=670218 http://news.ycombinator.com/item?id=1421698 http://news.ycombinator.com/item?id=1421698 http://news.ycombinator.com/item?id=1818166 http://news.ycombinator.com/item?id=1818166 Each of these has substantial discussion, and I'm pretty sure there are more.