There have been issues with physical Bitcoin in the past. Projects such as Casascius and Denarium had centralization issues and even risked key exposure, getting shut down due to regulatory concerns. One potential con here might be that, even while one is splitting the keys, part of the security still relies on trusting the issuer of the SEEDCARDs not retaining a copy of the partial keys-a risk which has been realized in physical Bitcoin implementations previously.

Have you considered at all how a user would actually know the issuer is unable to access the private keys after the fact of issuance? This might be somewhat alleviated by greater transparency in key generation or, better still, in an open-sourced framework, and it certainly appears that is a good start with your use of ECC software. It would also be useful to have some usability comparisons for SEEDCARD versus more established hardware wallets, which generally are considered the gold standard for security with Bitcoin because they are offline and have strong PIN protection. Though your offline generation process of a project is a big plus, delving a bit more into how it compares with pre-existing methods could help build a stronger pitch.

Thank you for taking the time to reply to my post.

The process of creating SEEDCARDs actually NEEDS the Issuer to retain a copy of a partial key (not both keys). Each key is generated in a different location. The 'spendable' part of the SEEDCARD is created by the Card Agent and both keys are only required when the SEEDCARD funds are swept and the card is physically destroyed. Every SEEDCARD has a unique NFC chip embedded to ensure that the Card Agent does not make multiple copies.

Totally agree on your points about open source and transparency in generating the wallet keys. All code will be open sourced on our GitHub - https://github.com/seedcard

When we have a MVP i will submit it for review with https://walletscrutiny.com/ I have taken a good look at the Bearer wallets whilst researching for this project.

Can I ask just for a moment, because I never thought about physical BTC - why would a person do that, not a cold wallet or something?
Privacy, full control?

 This is a good thread which may well help you

https://bt.irlbtc.com/view/5416519.0

What about the engraving process - could this be a weak link? Will it be off line?

https://i.ibb.co/Mgb0Fyn/SEEDCARD-key-generation.jpg

Diagram of Generator ECC wallet generation process.

Note that each coloured block is designed to generate an output separately - without requiring additional information (private keys).

@john_egbert SEEDCARD looks and feels like a metal credit card but the primary usecase is to spend like cash.

It is indeed for offchain transactions, and there is no useable private key so risks of third party theft are low.

SEEDCARD aims to be the 'cash' that Satoshi mentioned in his whitepaper.

SEEDCARD is physical BTC money that has the same characteristics as government issued banknotes... but without the centralization or unlimited supply.

It's a good idea, but I think it would be better to have two options with both plastic and metal cards.
Plastic card would be cheaper and it won't be detected on airports for people who are traveling and crossing border.
Can one Seedcard be used multiple times with different amount of coins?

This would have been a nice approach towards the Bitcoin initiatives it would have let everyone on Bitcoin since transactions could be done in this way as proposed in the article in an off-chain matter but somehow, I feel we should just let Bitcoin be what it was meant to be, an online transaction. A physical equivalent doesn’t really translate to value. In fact, I see certain challenges in this.

1. Now, the idea is off chain and needing less knowledge of its technicalities but still, you need technology for verification and authenticity. That’s technology right there.

2. Steel plates would be used and though, they might not be as much heavy, they still would come with some weight.

3. The use of NFC simply means, if I’ve got any of these steel plates on me, I would find just any device that supports NFC making the connections when close by or activated out of suspicion, which might range from criminal propaganda to what have you.

4. A question of denomination and balancing. Just how much worth of it would I be carrying about, how do I get the balance after a purchase.

These and possibly more are the challenges this system can face. How do we go around these, it’s hardly a system I would prefer to what we have now. I still prefer Bitcoin sticking to its digital, on chain and technical means to transacting. If anyone haven’t got much on its technicalities, what’s there to do is learn.