The controller unit of Mystery Box 001. For some reasons there are two leading zeros here, though I doubt I will ever reach a hundred mystery puzzles.

     This is the second Mystery Box I build, the first wasn’t documented as much but had great success – I decided to create a brief description in case someone decides to build one for someone. I have around one month to complete this but made some good progress as I write these lines – the box was designed (bottom lid still needs to be done) the LED matrix and buttons were built and it seems to fit quite well together. This is the first revision of this circuit and it’s built on a perf-board – there are a lot of wires hanging around but so far everything seems to work.

     The key belonged to a small cash box, I got two when I bought the box from a local shop. I put an Arduino-based main controller in it, the unit had a keypad and a simple 2x16 LCD inside. On the front panel there was a socket for an edge connector – that’s where some home-made printed circuit boards supposed to get inserted. 

     These small PCBs had some LEDs and a memory chip on-board. The memory chip was in fact a diversion as they had absolutely nothing written into them. My friend is an electrical engineer and probably knew at a glance that those were some EEPROMs. I wanted to have something funny in there, like “HA! Nothing here…” but gave up on the idea because it might had been a bit too boring for his kid to have to snoop around like that. Anyway, there were four different PCBs made and each one was coded with some resistive dividers so the Arduino could figure out which one of them is plugged into the blue connector.

     The idea behind this whole thing was to team them up for a small quest before collecting their prize - the prize itself was a symbolic LEGO gift they get once they solved every puzzle.

The contents of the box were the following:

     • A controller with a USB-UART converter

     • Some small gifts (matchbox)

     • A short letter

     • A PCB that fit into the blue connector, or as I called it, "Key 1".

     The keys were all password protected and I will share the ino file here once I figure out how to use the Sitepad editor correctly - it's coming.

1. Quest for Key 1

     The first PCB was in the cash box so they had that to start with but there was a six digit password, the name of my godson. That was pretty easy to guess and they got it quite fast. The code then proceeded to the “content” of this first key: a link to a Hungarian book about a couple of kids time traveling to save humanity. One of them was an undercover cyborg and was supposed to go alone but took a couple of his classmates with him. Anyway, the link was shown on the LCD and then some numbers popped up, four groups of two digits. These numbers coded the page, line, word and letter numbers my friend & his son had to write down to build up a sentence. I “forgot” to tell them how the whole thing works so they had to figure it out themselves. They got it quite fast and the sentence they put together pointed them to "Key 2" I had planted someplace in their kitchen. "Key 2" had a password as well, it was “dinosaur” in Hungarian.

2. Quest for Key 2

     "Key 2" points them to yet another book by Jules Verne “800 leagues on Amazonas” a great book as well. This book is about a guy who is about to get convicted for some stuff he didn’t do, but there is an encrypted letter that can save him and in the end it is finally deciphered. The code is “ORTEGA”. I used the exact same cypher to encrypt a message and show it on the display. They could enter random cyphers and the Arduino would decode my message using that cypher, but it would be gibberish if the wrong cypher was used. Entering the good cypher resulted in a message telling them that "Key 3" is at my friends daughter + what was the keyphrase they had to say to her in order to retrieve the key.

3. Quest for Key 3

     "Key 3" had a password which roughly translates to "donno", and I instructed the daughter to answer “donno” whenever they asked her what the password was. They got this very fast to my surprise but hit another password with a prompt: new password: "new adventure"! The password was of course “adventure”. Once they got that, a text rolled onto onto the display guiding them to the LEGO toy in their garage.

This is about the short of it, it took months of preparation and they nailed it in less than 24 hours!! They read through two books and had tons of fun! So much fun, that I decided to build another.