Remoticon Video: Breaking Encrypted Firmware Workshop

If only you could get your hands on the code to fix the broken features on your beloved electronic widget. But wait, hardware hackers have the skills to write their own firmware… as long as we can get the compiled binary into a format the hardware needs.

Luckily, we have Uri Shaked to walk us through that process. This workshop from the 2020 Hackaday Remoticon demonstrates how to decipher the encryption scheme used on the firmware binary of a 3D printer. Along the way, we learn about the tools and techniques that are useful for many encrypted binary deciphering adventures.

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Building A Resistor Substitution Decade Box

[George] built an incredibly tidy resistor substitution decade box. These devices feature a pair of connections and a way to select the resistance between the two of them. In [George’s] case it’s a pair of banana jacks and these eight thumbwheel switches.

What you see above is the side of each thumbwheel switch. These are panel mount devices which show one digit with an up and down button to change the setting. As you can see, the PCB for each provides connections to which a set of resistors can be mounted. This is the difficult part which he goes to great lengths to explain.

At this point he’s got the resistor groups for each digit soldered in place, the next step is to stack the switches next to each other and connect them electrically. From there it’s off to a project box in which they will be mounted.

This project does a great job of explaining the assembly process. If you’re interested in the theory behind a substitution box check out this other project.