Bitcoin Forum

What are the names of some of these devices again? I'm struggling to find them:

A year or three ago I came across various devices that had a private key inside them, holding a certain amount of bitcoin.
I think they ran off external electro-magnetically induced power (like a credit card) to power its chip, which could prove ownership of its key to an external device that had a new-enough copy of the blockchain for verification.
Like a hardware wallet it would destroy its private key if an attempt was made to get inside it, perhaps willingly exposing it after the HTLC time arrived?
I think they held a HTLC balance for proof of it being able to 'hold its value'.
I forget if they had a way to prove that a particular card was the only card that held that key. (I can't think of one; what would stop the manufacturer reusing the same key on more than one card? Possibly some way on the lightning network or similar? I've no idea.)

I searched for half an hour and failed to find them.
Anyone remember some of their names?

Thanks

By all this information and based on my understanding of smart contracts, you are not actually looking for a wallet but a contract type. But note that the Hashed Timelock Contract (HTLC) is a conditional smart contract that you have to follow promptly.

If I were you, I would rather go for the normal escrow service instead of this, unless you are considering the cost of multiple transfer and want to explore the likes of the Lightning Network through it.

Sorry, I think I meant Time Lock instead of HTLC's.
So that anyone owning or receiving this card device could check that the address in it could not be spent for like 5-10-20 years.
Personally I wouldn't bother with it, but I do find it an interesting application for bitcoin being used as a physical medium (like a fifty dollar note or a 1 gram bar of gold).

Are you referring to hardware wallets such as the Ledger or Trezor. Because with them, you will be able to make use of secure elements to hold your private keys while proving the ownership without having to disclose the key.

I think you might be talking about OpenDime or the newer and updated version called SatsCard.

OPENDIME: https://opendime.com/
SatsCard: https://satscard.com/

Both are manufactured by CoinKite and can be found here along with all of their other products: https://store.coinkite.com/store

I think you should be talking about   Casascius (https://bitkan.com/learn/physical-bitcoin-how-to-tell-if-a-physical-bitcoin-is-real-4564) if am right about your guess then here are some vital threads already discussed about this physical bitcoin on the forum

https://bitcointalk.org/index.php?topic=51964.0
https://bitcointalk.org/index.php?topic=39306.0
https://bitcointalk.org/index.php?topic=52537.0

You can make more research on that if i just made the right guess, casascius is a physical bitcoin and all you could needed to use in claiming this bitcoin token wrapped is in the definition of what casascius is and how to redeem it.

OpenDime, SatsCard and Cacascius; yes that's what I was looking for. Thanks

IMO you were talking about Tangem cards instead, AFAIK, they use to be the first ones to launch this kind of magnetic NFC cards. Other companies has offered similar products after them, but the first and the most known commercial brand is Tangem https://tangem.com
Why are you looking for this kind of product by the way? It's less safe than a hard wallet obviously, and if you want to use it in order to make an offline transaction by giving one funded card to someone, your recipient needs to know this technology and to trust it along with you.

Paper wallets could also do something similar because they have printed private key, and there is also several projects that made bitcoin paper notes that look great and can be used the same way like cash.
Here is one of them called offline.cash, I think I remember them from bitcointalk forum, but only reservations are available.

Just interested in the novelty of being able to physically trade a valuable private key, that is locked say for 10 years or 100 years, that can be verified without needing an internet connection, that destroys itself if opened before the 10 to 100 year time has passed. I guess a list could exist to ensure that the used address did not exist anywhere else. But yes still some trust given to the manufacturer I suppose.

Are talking about, Trezor Model T and Ledger Nano S/X,   or Opendime looks like a physical USB stick-like device.