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This part of the article explains more: https://en.wikipedia.org/wiki/Restrictions_on_geographic_data_in_China#GCJ-02 https://en.wikipedia.org/wiki/Restriction

by acqq 11y ago

This part of the article explains more: https://en.wikipedia.org/wiki/Restrictions_on_geographic_data_in_China#GCJ-02 https://en.wikipedia.org/wiki/Restrictions_on_geographic_dat... "GCJ-02 (aka Mars Coordinates) is a geodetic datum formulated by the Chinese State Bureau of Surveying and Mapping, and based on WGS-84.[12] It uses an encryption algorithm[13] which adds apparently random offsets to both the latitude and longitude, with the alleged goal of improving national security.[14][15]" "Despite the secrecy surrounding the GCJ-02 encryption, several open-source projects exist that provide conversions between GCJ-02 and WGS-84, for languages including C#,[20] C, Go, Java, JavaScript, PHP,[21] Python,[22] R,[14] and Ruby.[23][24] They appear to be based on leaked code.[25]"

ex3ndr 11y ago
Interesting that there are actually no encryption at all, just simple math equations.
- chias 11y ago
  > just simple math equations To be fair, you could say the exact same thing about any modern encryption scheme.
  - GavinMcG 11y ago
    "Simple" is... debatable. There's a good reason rolling your own is a bad idea.
    - teambob 11y ago
      The 'how' of encryption is often quite simple - it is 'why' that is difficult
      - reitanqild 11y ago
        Or the other way around? Example: We all know why we should protect against timing attacks. How to get it right is the harder part.
  - nl 11y ago
    No. Encryption is designed to be irreversible without a specific piece of extra data. That isn't the same as not knowing the formula or initialization seeds used. Those are both reversible.
- colechristensen 11y ago
  I'm going to assume from the context is what they actually did was use a crypto-grade RNG to introduce bumps into the geoid surface. That is, instead of everything being 2 meters to the west (or whatever) things were randomly offset from their reported positions. You could "map" the whole thing or somehow steal the source and crypto parameters in order to transform between geoids, but you couldn't do something simple like subtraction.
  - acqq 11y ago
    However it was obviously their goal not to have completely random oordinates but just "less precise."
    - colechristensen 11y ago
      Not random ordinates, unpredictable offsets, apparently on the order of a kilometer. And it wasn't precision they were after at all. You could just make a global positioning system arbitrarily less precise but that isn't useful. Kilometer precision doesn't have much use to civilians, they need meter-precision at least and repeatable at that. What they were after was unpredictable but static accuracy offsets which presumably could be altered in a crisis.

by acqq 11y ago

ex3ndr 11y ago

Interesting that there are actually no encryption at all, just simple math equations.

chias 11y ago
> just simple math equations To be fair, you could say the exact same thing about any modern encryption scheme.
- GavinMcG 11y ago
  "Simple" is... debatable. There's a good reason rolling your own is a bad idea.
  - teambob 11y ago
    The 'how' of encryption is often quite simple - it is 'why' that is difficult
    - reitanqild 11y ago
      Or the other way around? Example: We all know why we should protect against timing attacks. How to get it right is the harder part.
- nl 11y ago
  No. Encryption is designed to be irreversible without a specific piece of extra data. That isn't the same as not knowing the formula or initialization seeds used. Those are both reversible.
colechristensen 11y ago
I'm going to assume from the context is what they actually did was use a crypto-grade RNG to introduce bumps into the geoid surface. That is, instead of everything being 2 meters to the west (or whatever) things were randomly offset from their reported positions. You could "map" the whole thing or somehow steal the source and crypto parameters in order to transform between geoids, but you couldn't do something simple like subtraction.
- acqq 11y ago
  However it was obviously their goal not to have completely random oordinates but just "less precise."
  - colechristensen 11y ago
    Not random ordinates, unpredictable offsets, apparently on the order of a kilometer. And it wasn't precision they were after at all. You could just make a global positioning system arbitrarily less precise but that isn't useful. Kilometer precision doesn't have much use to civilians, they need meter-precision at least and repeatable at that. What they were after was unpredictable but static accuracy offsets which presumably could be altered in a crisis.