CrossCTF_2017: Time To Take A Dump

Category: Hardware Points: 200 Description:

There seems to be something running on the FREE arduino! I wonder if I can talk to it...

Write-up

I'll start off by saying I have 0 experience with hardware and am a complete noob. However, I have Google. Firstly, we need to accomplish dumping the flash memory of the Arduino Mega, accomplishable through avrdude.

Afterwards, we need to convert it to hexadecimal format for easier reading through using avr-objdump. From there, we can see a few interesting strings, like a very sneaky fake flag, a string that suspiciously looks like an encoding table and the original encoded string. After a little bit of twiddling, it does seem like a base64 encoded string but not in the same form as the base64 we all know and love.

So, this is a case of custom base64. Using a site recommended over at zst123's GitHub, we can decode the flag to CrossCTF{Bas364_1z_hard}.

Therefore, the flag is CrossCTF{Bas364_1z_hard}.

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