Secret Dual USB Data Vault




About: Professional work in various electrical and mechanical fields, obscure sense of humour and typically willing to help... Currently under contract designing environmental monitoring equipment.

Entering the correct combination on ths drive allows you to depress the button on the rear of the drive to extend the USB 3 plug for insertion into the USB port on a computer and look at the information contained on a 32Gb memory stick...

At least that is what everyone will think.. However entering the correct second 5 digit combination with the connector extended will allow you to access the secret 32Gb hidden drive within where the real information is stored.

That's 3 lines of defence

  1. 5 digit combination lock to extend the USB connector and look at the 32Gb drive contents
  2. ignorance that a second drive exists
  3. different 5 digit combination to access a hidden 32Gb drive

The shell protects the delicate electronics and inner workings from prying eyes. It is sealed with adhesive to prevent opening. The number rings are solid and the combination is hard coded.

Locking the drive is a simple matter of depressing the USB connector back into the housing.

Step 1: Void the Wty on Your USB Drives

I used 2 Kingston 32gb USB 3 type drives for this. I selected these for the local availability, size and price since I knew that I was going to be destroying them to make something great.

I pried the protective shell off to reveal the inner circuits.

These will both have to be modified by removing the VCC power pin from the circuit board. This is pin 2 in the case of the USB 3, 9 pin architecture. checking the datasheet for a connector will show this..

For sizing, one of the drive input connectors has to be removed... Carefully!!! I used a hot air style soldering iron for this and the connector literally fell off the board.

I used wire wrap style wires for this next part.

All of the drive pins connected together between the dummy and secret drives, with the exception of the power pin.

On the circuit board side of both drives there needs to be a wire connected to position 2, this is the VCC power for the drives. do not connect it to the power input from the USB connector it needs to be completely isolated from the power input.

A jumper wire is then soldered to pin2 of the USB connector. This wire will eventually feed the power back to the drives and also power the control circuitry, for now leave the power wires disconnected.

The mess of loose wires here has 6 wires not connected at both ends, 2 black 5V from the USB connector. 2 yellow for ground, and one white for power to each drive.

Step 2: Parts

Using the included files, print the parts needed for the drive.

There are 5 digit rings needed, 5 spacers, 2 end caps, 1 locking rail and 1 internal board holder

I have included 10 number combination rings here.

Step 3: The Digit Rings and Unlocking...

The digit rings have two unlocking features.

The first is the standard combination style lock which is just a space or opening in the inner ring.

The second is a bevelled lump which will provide mechanical input to the lock circuitry.

Step 4: Electrics, Circuit Description and Partial Assembly

I usually start the physical design first then make the electronics fit, this limited my choice of switches drastically and I had to use tiny tactile switches that were underrated for the tiny relay I needed to use.

to correct this I had to use the switches to drive a transistor to switch power for the relay coil to avoid burning out the switches which were rated for 1mA each.

The circuit uses the USB input power through 5 switches wired in series. There is a 1k resistor in series with the switches which drives a tiny transistor to activate the coil of a relay.

The relay in normally closed position will send USB input 5V to the dummy drive. When the switches are all closed and the relay coil activates, the relay will then shut off dummy power and apply power to the secret drive.

Each switch is held in place with adhesive in the selector ring as shown.

Each digit ring is then placed onto the selector ring taking care to slide the ring lump through the cutout. mind the orientation of the rings and note the opening combination.

It is easier to solder the switches together as each ring pair is glued to the next.

When all the rings are fastened together the circuit must be tested prior to final assembly.

Step 5: Mechanical Internals

The internal drive carrier is assembled as shown with an end cap and locking slide.

The locking slide has bevels on it so that the drive can be locked with the rings out of position.

Ideally the slide will have springs to hold it in place, I did use foam weatherstripping as a suitable replacement. The foam compresses to allow the slide to collapse and then springs back to its original position to pressure on the slide.

The rear of the carrier has a button cap attached which is the same colour as the housing. this has a flange to prevent the drive from retracting too far and also to prevent any physical access.

There are tabs for the USB drive to lock into place and a cutout for the relay.

The Dummy drive is placed in the cutout with the chip side down. a small insulation layer is placed then the secret drive is stacked on top of it. I used 2 side carpet tape.

These are all held in place using non conductive adhesive. I used hot glue but that is not an ideal solution.

Adhesive was also used to eliminate all loose and hanging wires.

Step 6: Final Assembly

The rear cover is keyed to allow for proper alignment.

With all the drive parts in place the rear cover is glued in place using abs solvent cement.

The front of the drive also has internal keying but it will not engage the spacer ring since I needed the extra 1mm for internal clearances.

It is put in place using friction fit and the drive is tested for mechanical and electrical operation.

If satisfied, remove the front cap then glue it in place using solvent cement.


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    23 Discussions


    4 months ago

    Super cool! Would love to see a video posted of it in action!


    Answer 4 months ago

    Give the content a quick read, you extend the drive by keying in the correct code and the can access the hidded drive by keying in a separate code. There are two fully functional drives.


    Question 4 months ago

    Would other USB drives work?

    1 answer

    Answer 4 months ago

    I have only checked a couple of different drives and found that there are some differences between manufacturers which would make drop in replacement a hit and miss prospect.
    I had a couple of older Kingston drives (8Gb and 16Gb) and the board inside of those has the exact same footprint as the ones that I used.


    Reply 4 months ago

    I don't think so, I think the code is set by the rings you insert.
    Maybe you can take it apart to change rings.


    Reply 4 months ago


    No, it is hard coded, the only way to change it is to crack it open and replace the rings. Also I have included only 10 of 90ish possible ring combinations


    Reply 4 months ago

    Awesome! Thanks for the update! How would I go about making a different combination? Moving that small "bump"? Thoughts?


    Reply 4 months ago

    Certain configurations are not available like 0-0 , 1-1, etc.

    Since the code rings are printed solid, the files have to be modified with a CAD program to adjust the code. The adjustments are as simple as changing an angle in the drawing and rebuilding the file. If you are having trouble with this, send me a message and I can send you the drawing file


    4 months ago

    Excellent, actually something I would want to keep safe.


    Tip 4 months ago

    To reduce the complexity you could have wired only the D+, D-, GND and VCC wires. You would have lost the USB3 speed on the second drive, but... who needs it on a 32GB drive?
    Regarding the project, instead of a relay (which is large) you could have used just two MOSFETs
    For the rest, good idea and good execution :)

    1 reply

    Reply 4 months ago

    Than you.

    As I explained I only used 32Gb due to local availability and the idea here is to use larger drives in the future so I wanted to see if this would work fully. which it does.

    Using MOSFETs here was not good idea since I was going for complete electrical isolation, simplicity and I find that hand soldering tiny components in dead bug configuration is problematic to say the least.


    4 months ago

    Wow, talk about 64GB in a five pound bag!
    Nice idea, nice design, beautiful implementation.

    and I t’s not really a dummy drive. It works, right?
    so you have two selectable drives.

    the dummy drive is for your “protected work” stuff.
    the hidden drive is for your NSFW etc. or the manuscript on how you have developed cold fusion...

    One caution,
    your drives are identical.
    the probably present the VID (vendor ID) and PID (product ID) to your os.
    if they are the same (and you can verify this from hardware manager on one of the pull downs on the drive) I think you risk the os getting confused if you ever switched drives with it plugged in - the system might not notice the change - does it “di-dunk” and then “do-dink”?
    if so, it probably noticed the drive change, but your not out if the woods.

    you didn’t eject the dummy drive before switching which can be bad.

    strongly suggest setting to the desired drive before inserting.
    eject when done.

    if you want to change drives, eject the one that’s inserted, code in the second and reinstall.

    of course eject that one when done.

    1 reply

    Thank you. Yes the dummy is a fully functioning drive, I guess i should have called it decoy or something like that.

    Your concenr is definitely valid


    Question 4 months ago on Introduction

    I'm 65, on disability, live in an apartment, own enough stuff to hang pictures level, and can cook my head off. To make this? Not a chance. So, how much will you charge me to make one for me? I need this to put some documents in my safety box at the bank, so only the executor of my will can access the real stuff.


    Tip 4 months ago

    This is an interesting but complex project. I do recommend using a spelling checker or ask someone to do a proof read before publishing. You missed "coin" for "coil" and "UDB" for "USB". This happens to many of us but a proof read will prevent the errors from being published.

    1 reply