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Eurydia / project-dsp-calculator

Dyson Sphere Program tool for calculating production per minute.
https://eurydia.github.io/project-dsp-calculator/
MIT License
3 stars 1 forks source link

Schematic generation #31

Open Eurydia opened 2 months ago

Eurydia commented 2 months ago

The last feature to complete this project is an option to build a dynamic blueprint. It is clear that blueprints in Dyson Sphere Program is an encoded string along with some metadata. The metadata is comma-separated, and the actual blueprint information is present as the payload.

Reversing engineering the blueprint encryption and decryption will undoubtedly be the most time consuming part of this feature.

Eurydia commented 2 months ago

A preview of the blueprint is also needed as a complementary feature for this update.

Eurydia commented 2 months ago

Upon investigation, I have discovered the anatomy of a blueprint. Note that a the header section of a blueprint is mandatory due to the checksum.

BLUEPRINT:0,10,0,0,0,0,0,0,638494904957092655,0.10.29.22015,New%20Blueprint,"H4sIAAAAAAAAC2NkQAWMUAxh/2dgOAFlMsKFEWpPrDHHxv7P4cjwHwpQTWZgAAADD8pdcAAAAA=="E6DED3AAC6C334AE4D6FC6E17ECDF5D0

Firstly, the following section will be referred to as the header. It contains metadata about the blueprint itself.

BLUEPRINT:0,10,0,0,0,0,0,0,638494904957092655,0.10.29.22015,New%20Blueprint,

The first few comma-separated numbers represents the icon layout and icons. They determine which icon layout, icons, and icon positions to display on the in-game menu. The long number represent the time of creation of the blueprint, in seconds since last epoch. The game version in which the blueprint is created. Lastly, the name of blueprint.

However, the name of the file does not need to match the name of the blueprint. For example, the file could be call BP, while the blueprint name is RP.

The section is the actual content of the blueprint.

"H4sIAAAAAAAAC2NkQAWMUAxh/2dgOAFlMsKFEWpPrDHHxv7P4cjwHwpQTWZgAAADD8pdcAAAAA=="

So far, this section contains the building layouts, placements, configuration as well as their coordinates on the planet. The section is encoded using base64. For this section, it is good idea to build and improve upon existing findings; https://github.com/johndoe31415/dspbptk and https://github.com/Wesmania/dspbp.

Finally, the last part is the hash.

E6DED3AAC6C334AE4D6FC6E17ECDF5D0

The hashing algorithm appears to be a modified version of MD5. The hash works by taking the entire content, both header and payload, and append the hash to the end of the string.

Eurydia commented 2 months ago

The actual payload base64 encoded and gzipped. As such, it should be decoded using base64, and decompress using gzip. The result is a byte string. It cannot be processed any further, so the only way to progress is to match it with existing byte data of buildings, settings, configation, etc.

H4sIAAAAAAAAC2NkQAWMUAxh/2dgOAFlMsKFEWpPrDHHxv7P4cjwHwogImxwUwFEf9RQcAAAAA==

After decoding and decompression, the following byte string is obtained:

\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x01\x00\xff\x00\x00\xc8\x00\x00\x00\x00\x00\x01\x00\x01\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xc8\xac7\x00\x00\x00\x00\x00\x00\x00\x00\x01\xc8\xac7\x00\x00\x00\x00\x00\x00\x00\x00\xff\x08A\x00\xff\xff\xff\xff\xff\xff\xff\xff\x00\x00\x00\x00\x00\x00\x06\x00\x00\x00\x01\x00\x00\x00\x00\x00
Eurydia commented 2 weeks ago

The next step is to interpret the byte stream and understand how it stores the information of a blueprint, which will be the most demanding task of the entire feature.

Hopefully, understanding the byte steam will allow me to peek into how a blueprint is generated and create one of my own. Afterward it is just a matter of retracing in the form of compression, encoding, and hashing the stream.