This seems like a VERY cool technical solution in a desperate and fruitless search of a problem.
> They consist of a flexible circuit board, specialized secure element chips and an independent NFC interface capable of powering the secure element. Each secure element stores an internally-generated ECDSA key pair that is associated with a unique smart contract on the Ethereum blockchain
Who wants bills that cost $3 ea, and are not likely to survive a wash?
> flexible circuit board
FPC != "meant to be constantly flexed". Most are not designed for a certain (not small) bend radius and to be bent no more than a dozen times. They are more meant to be curved once into a particular shape than to be constantly bent.
> I2C, raspberry pi connector
That will do great with dry pockets and ESD
> raspberry pi connector
tiny holes, so your notes can catch on your keys and any other thin sharp object in your pocket
Glad you think it's cool, given your background that comment means a lot to me personally.
I would contend it's not "in search of a problem" but trying to solve one. Specifically the usability nightmare that is cryptocurrency. Cash has tradeoffs but it has great usability properties. The space needs rebalancing in that direction.
Linen notes last about 4,000 bends before breaking, FPC lasts about 6,000. The stuff thats critical to validation is not in the 'bendy bit' pathway.
Did some ESD testing but the NFC chip bears most of the brunt here and not the secure element. Likewise the tiny holes dont bug me so much as the QF Packaging. Want to go slimmer in our next revision.
But, how tests are done differs from what bills face: Large curve radius, slow curving, nothing sharp poking at it in the middle. Basically the opposite of what is going on in tight pockets/purses.
> NFC chip bears most of the brunt here and not the secure element.
Unless the dielectric over your secure element is some previously unknown type, a few kilovolts will arc right through it and hit your secure element.
The 6,000 number is creasing the kapton 180º over the course of half a second with the 6mm curve radius. Copper breaks but not the lines critical for validation.
Our goal wasn't to make this thing indestructible, it was to figure out where the bar was for "good enough".
USD benchmarks are roughly:
4000 folds
2 years lifetime (low denomination)
8 years lifetime (high denomination)
30 transactions before decirculation
For Kong we aimed for:
6000 folds
10 years lifetime
unknown number of transactions before decirculation. (Unknowable)
Survives a wash
I think it's sufficient for what Kong is now but we have ideas for improvement and I would love here yours. Specifically anything we could do on the ESD side.
We've met before years ago but if you would like to get some to play with please email me.
> They consist of a flexible circuit board, specialized secure element chips and an independent NFC interface capable of powering the secure element. Each secure element stores an internally-generated ECDSA key pair that is associated with a unique smart contract on the Ethereum blockchain
Who wants bills that cost $3 ea, and are not likely to survive a wash?
> flexible circuit board
FPC != "meant to be constantly flexed". Most are not designed for a certain (not small) bend radius and to be bent no more than a dozen times. They are more meant to be curved once into a particular shape than to be constantly bent.
> I2C, raspberry pi connector
That will do great with dry pockets and ESD
> raspberry pi connector
tiny holes, so your notes can catch on your keys and any other thin sharp object in your pocket