I wouldn't trust it for sums worth paying $10/card for unless it uses something like Shamir's Secret Sharing or the BIP-XX(?) that Casascius has talked about using. That is, there should be a way that I can order a card and you only ever see part of the private key so there's no way you could steal from the account. Simply asking customers to believe you have destroyed the copy you have is insufficient.
I do like the idea of using stainless steel as long as the data is stamped into the card and not simply printed onto it. The metal might be able to withstand high temps, but the ink likely would not.
Shamir's Secret Sharing would defeat the purpose. The crad is supposed to hold the key and keep it safe, if another peice of data is needed, what's the point.
Speaking of Casascius, his physical coins are made in the same way, he has to see the keys. Obviously he has earned the trust, but will you ONLY ever trust products made by him? That being said, I'm open to suggestions for how to reassure customers since it is a valid concern.
It would either be engraved or printed using a glass based method. Whatever I decide on, I will ensure that it is fireproof up to AT LEAST 1750 degrees Fahrenheit.
I do have one possibility, but it would require that I get 200 preorders. What if the customer generated the wallet and sent me all but the last 8 digits of the private key? I could then print that on to the card and require that 8 digits be memorized.
You should make it so that customers can add the private key themselves for security.
If you have any ideas on how this could be done in a way that doesn't require the customer to have any equipment and yet would be permanently and securely affixed let me know. However, I don't really see this working.
Got one for LTC? Have you considered a private key that only would display when heated?
If all goes well on the Bitcoin model I could make some for LTC, however, they would likely cost more due to less demand.
I will look into that, but I am not sure that there is an affordable yet secure way to do so.
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yea not a huge fan of the fact that the privite key is clearly visable. I think the privite key should be on the back or on a one time scratch off pad or something. Even something as simple as a door that covers the privite key so that someone can send to you without seeing the privite key
I am definetly leaning toward covering it with a scratch-off or hologram right now.