> The token is durable enough to survive on a key chain for years, even after going through the wash.
On the other hand, the token is shown as "naked electronics", without a husk.
Is that really sufficient for such a device? Does it really withstand (mineral) water, mechanical stress (key chain), let alone the combination of both (washing)?
All of the parts have a low center of mass with respect to the PCB and are unlikely to catch on anything. Water and/or sweat won't hurt it as long as it's dry when you use it. I've tested it works fine after putting it through a washer and dryer.
However, making your own casing or 3D printing something like this [1] is always best
[1]: https://github.com/conorpp/u2f-zero/blob/master/hardware/cas...
First things to fail will be ceramic capacitors torn/cracked and leads of SSOP-20 package bent/shorted.
That said, it is trivial to protect the board from all of above - just wrap it (except USB connector) with insulating tape or better yet, cover with silicone putty, or similar.
(In dutch, sorry, but you'll be able to find similar stuff all over the world)
I think it would be tough to break the board, so mechanically the worry would be bending some pins such that they shorted.
I have no idea what the ESD sensitivity of the parts is, but if it's something your going to walk around with in your pocket, that's something to think about. I'd probably use some heatshrink tubing on it.
There is an ESD diode in the design but it only protects certain pathways -- a zap could come from anywhere if the thing is bare.