radio drw0if, marcog

Welcome to our virtual satellite!

The following endpoints allows you to retrieve the 3 parts of the full flag:

Link layer at :10015 Channel coding at :10016 Modulated signal at :10017 Please read the attached file carefully to get how the communication stack is built and how to use the taps provided at different parts of the stack.

Stack Building

Welcome to mHACKeroni Virtual Satellite!

This satellite follows (almost) all the specification listed in the following blue books: - TC space data link protocol: for the uplink data link - TM space data link protocol: for the downlink data link - TM synchronization and channel coding: for the channel coding - BPSK as modulation

Our stack is as composed:

RX Antenna
    X
    |
    |    ____________       ______       _____________      _____       ______________       _____________
    |   |            |     |      |     |             |    |     |     |              |     |             |
    +---| BPSK demod | --> | Sync | --> | Descrambler | -> | FEC | --> | Frame parser | --> | Application |
        |____________|     |______|     |_____________|    |_____|     |______________|     |_____________|


                                                                                                  TX Antenna
                                                                                                       X
                                                                                                       |
     _____________       _______________       _____      ___________       ______       __________    |
    |             |     |               |     |     |    |           |     |      |     |          |   |
    | Application | --> | Frame builder | --> | FEC | -> | Scrambler | --> | Sync | --> | BPSK mod |---+
    |_____________|     |_______________|     |_____|    |___________|     |______|     |__________|

Taps

In order to help with the debug in the various step we built some taps that you can use to access intermediate part of the stack.

Link layer

Using the service at port 10015 it is possible to directly access the data link layer and exchange TC and TM frames directly:

                     ______________       _____________       _______________     
                    |              |     |             |     |               |    
    taps:10015 ---> | Frame parser | --> | Application | --> | Frame builder | ---> taps:10015
                    |______________|     |_____________|     |_______________| 

Channel coding

Using the service at port 10016 it is possible to directly access the channel before the modulation takes place, you get a plain bitstream:

                    ______       _____________      _____       ______________       _____________
                   |      |     |             |    |     |     |              |     |             |
    taps:10016 --->| Sync | --> | Descrambler | -> | FEC | --> | Frame parser | --> | Application |
                   |______|     |_____________|    |_____|     |______________|     |_____________|

     _____________       _______________       _____      ___________       ______     
    |             |     |               |     |     |    |           |     |      |    
    | Application | --> | Frame builder | --> | FEC | -> | Scrambler | --> | Sync | --> taps:10016
    |_____________|     |_______________|     |_____|    |___________|     |______|     

Full experience

Using the service at port 10017 it is possible to access the virtual antennas of the satellite, you get a stream of complex.