Integrate apps with the Tangem Card?

Hello everyone.

I have recently been sent the Keycard* for development purposes and I have created a demo app just to get used with the documentation (short video here)

*is a card similar to the Tangem card but for multiple cryptocurrencies at once

My questions, to someone that used the Tangem card before, is:
a) Would it make sense to integrate third party apps/wallets with the Tangem card? I ask this because they have their own app.
b) Is there a store from europe to buy a Cardano Tangem card? (I know about cryptosupreme but I’d pay more for shipping than for the card)

Thanks for your time!

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Well let me weigh in here just a little, I am an advocate for Cardano and have several Tangem card’s in my possession that I have plans for to promote Cardano, from my perspective if there was a legit Cardano app that the people I give these card’s to were able to use through the card they were given for Cardano focused project’s then I would not have to spend time trying to help them understand why Cardano is better than other Crypto project’s (I have spent countless hours trying to help some people understand this), I have not used the card yet myself - mainly cause I am lacking a place to use it in the U.S., so any app that is Cardano focused will be a benefit to our community and would likely drive the adoption of the card as well as benefit our community through giving them options, if I was lucky enough to meet someone where I am that was willing to accept Cardano as payment and was also set on using Cardano focused apps then such an app would be a great benefit to us,.
I think a Cardano focused app will drive the use of Cardano.
I am going to give an idea here:
I think it is possible for an app developer to build an app that is tied to a pool and would allow them to use pool owner profits to introduce discounts and rewards when the app is utilized, lot’s and lot’s of coding to make it happen but it surely is possible - profits might seem small at first but hey… if you make a wage while operating an app how much profit you bring is up to your creativity, right?
Private apps for Cardano have been touched on before but there has been nobody that has really pushed it through to large scale - I once was able to convert ADA into a amazon code with ease, with no problems at all- that was cool! Loved it! I love to see people work on apps and such if you were to notify me that you developed an app I should check out, man… I would be on it, so I hope you dig in and work on something that is b#@#$$, and let me know how it goes, message me, let us all know what you have going on i several threads so it is not overlooked. :wink:

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Here’s my take:

a) I would love to see third party apps for Tangem cards. My opinion is allowing third party apps allow for a wider selection of styles and features than what the Tangem developer team offers. It would also be nice if these crypto cards can be used as a hardware 2FA.

Some concerns of mine:

Is it fine for everyone to know the method the Tangem app uses to sign transactions?

I know the private keys are “embedded” (can’t think of a better term) to the chip itself and irretrievable by any user. Does the method/algorithm the Tangem app uses to sign transactions from the card’s chip use a hash function? a zero knowledge proof? is it open source? Can it be reverse-engineered back to the chip?

Tampering transaction details before sending to the blockchain

There’s also the risk of unverified/unsecure apps that can change transaction details, such as receiving address and amount to be sent, behind the scene while pretending to complete your intended transaction.

b) Try contacting the Cardano Foundation. I think they are based in Switzerland, so in Europe.

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Yeah, to me that is the big issue… since the card does not have a screen for us to check the transaction details a malicious developer may just replace the destination address or amount with different ones and you will blindly sign it.

I like your take and am glad to see questions being asked, your concern’s have validity and provoke thought, what comes to my mind is the question of whether or not anyone needs to know the method Tangem uses to sign transactions to connect an app to draw from the card, I am going to look into it after I have a chance to mess around with my card.

On the software side there is (almost*) no magic in the Tangem cards. It is just a normal wallet without providing a backup of the seed words.

It is fine to know how they sign transaction, they do it like every other wallet - because, like every other wallet, they need to implement Cardano specs otherwise the network nodes would reject the transactions.

*: almost because theoretically Tangem cards support reading out the amount of the card without being online. Therefore the store some kind of magic value directly on the card when creating / loading the wallet the first time.

This feature would make offline transactions possible (by handing over the card) but is currently not available for Cardano cards. And this is the main reason why the card don’t give you a backup seed. You do not want the person who paid you with the card to later restore the wallet via the backup seed words.

Check out my comment here: How to: Use a Tangem Card

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