With various governments passing laws demanding access to your encrypted data 1), 2), 3), it is time for some 'security by obscurity.'

This 'Ible is about making a USB flash drive which looks just like a cable. You can drape it out the back of your desk, leave it lying on the floor or coil it up and store it in your magic knot of cables. (If you don't have a magic knot of cables, then start collecting now: you can never have too many random cables.) Once the cable is where folk expect to see a cable, it just becomes invisible and your data is safe (well, safer).

For this, you will need

one of the mini USB flash drives which are not much bigger than a USB connector
cheap donor cable
a craft knife or a wide-bladed chisel
a pair of pliers or wirecutters
suitable glue (polystyrene cement, hot melt, cyanoacrylate or epoxy)
either a small spring clamp, or five minutes to spend holding things together.

I bought my donor cables from the local Two Dollar shop, but these ones look like they'd work.

For the USB flash drive, there are all sorts of options around. I found these two on AliExpress while I was writing this 'Ible.

Cheap ones
Expensive ones

I have no connection with any of the above links. They are just the result of a quick search for something which looked like I had used.

Step 1: Strip the Drives

There are two good reasons to choose the cheapest drives you can find. Firstly, the more expensive "Name" brand ones often have the capacity etched onto the metal of the connector which can be noticeable if you are looking for it. Secondly, the cheaper the drive, the cheaper the housing. With the drives I used, the plastic of the molded housing did not adhere to the metal of the connector at all.

I braced the drive on a piece of scrap wood and gently slid a chisel down the connector and into the plastic covering. That pared off one side of the plastic and the whole shell could be removed, leaving two small bits of scrap plastic and the core flash drive as seen in the third picture above.

The downside of using cheap drives is their lower reliability and the possibility of data loss. "If you only have one backup then you don't have a backup." But security, ease of construction and low-cost should allow you to make several devices and have multiple backups.

Step 2: Crack the Cable Shell

If the donor cable has a cover which is in two parts, gently work the blade of a chisel into the join and slightly twist it to pop the two halves apart. Even if the shell halves were glued together this should be enough to break the bond. This is another good reason to choose the cheapest cables you can find, as they are likely to have cheaper and weaker assembly methods.

Once the shells are separated, use a pair of pliers or wire-cutters to remove the old connector. Make sure that you leave whatever interaction there was between the cable and the strain relief, as that is what will hold the whole thing together. The third and fourth pictures above have the relevant bits highlighted.

Step 3: Or Cut the Molded Plug

Some of the cheap cables (most actually) have a plug cover which is molded onto the connector. (From which one can assume that this is a cheaper production method.)

I used a newly sharpened chisel to cut down through the rubbery plastic to the metal housing of the plug. Using a wide chisel meant that I could align the cut with the mold-line of the plug. Having the split on the mold-line makes it harder to see any imperfections when the plug is glued back together.

Once the cut is far enough along to enable the rubber to be peeled back, get in with a pair of pliers and cut the wires holding the old connector. If you can't reach down far enough, it might be possible to disassemble the connector in situ as shown in the last two photographs above.

Step 4: Assemble

Then stick the drive into the emptied plug using an appropriate glue.

I've used different glues with different host plugs.

The smooth plastic shells which pop-apart glue well with either superglue (cyanoacrylate) or polystyrene cement, while I've found that I needed hot-melt glue to get a decent result with the more rubbery plastics. Two-part epoxy would probably work well with both, but is a nuisance to use.

If you are using a melting-glue, the "CoolShot" brand which melts at a lower temperature is useful. It seemed to remain soft for longer while assembling the drive and shell, and worked with thinner layers than the ordinary hot-melt glue, which left a better-looking joint.

(I have no connection with CoolShot either)

Step 5: Conceal the Results and Conclusion

Now you have a cable where one end is a concealed flash drive. If it were plugged into a machine, then the OS would probably recognize it as a memory device and report that fact, so we want to reduce the chance of that happening. Tying the cable up in a bundle and putting a note on it saying that it doesn't work properly should deter most folk from trying it. Having a reputation as a bad person from whom to borrow cables is also effective.

Some final notes:-
some of the cables I used had a fabric covering, and this did not respond well to the treatment, as can be seen in the second photograph above. This might actually add to the plausibility of unreliability attached to the hidden cable.
it's not just printer and charger cables:- i even found a cheap PS2/USB connector which was changed (third photo)
having a variety of different cables makes it easier to remember which archive is stored on which device, and also provides a believable nest of cables.

Good luck, and do post a photo if you try it :-)