As part of our Methodology, we ask:
This product still needs to be evaluated some more. We only gathered name, logo and maybe some more details but we have not yet come to a conclusion what to make of this product.
The Analysis ¶
This does not represent a full code review.
The repository for the Tangem Android app is now available.
The app is now for verification.
Update 2022-08-01
This app is the companion app to an NFC card that is promoted as something like a hardware wallet but without a screen or a button it can only do what the companion app - this app - tells it to do. As such, this app is very crucial if you use these cards as your Bitcoin wallet. It has to be trustworthy and thus we consider it a Bitcoin wallet. Our mission is to look for the potential of all the users of an app lose all their funds at once which arguably cannot happen in the given configuration. The app could not collect the private keys from the cards if the cards do what they claim which cannot be publicly verified neither but even if the card does as advertised, the app could still steal a lot of funds of a lot of users if it would switch to evil-mode for all users at once. It would still require users’ interaction but the window of opportunity could easily be days to weeks before Google would remote-wipe the app or the app would get stopped from emptying wallets of unsuspecting users upon their next use.
The description on Google Play is not explaining much and talks more about issues with NFC of some phones and neither does their website explain in clear words what this app is but I found this demo video and it clearly shows that the app is crucial for the security of your funds.
Ironically if the app works the same on Android and the “copy address” part is actually copying the address to the clipboard which makes sense if one would want to send coins from an exchange to the card for example, any other app on the phone without any special permissions without even being apparently active could swap the receive address and the user would have no way of knowing this was happening.
Anyway, the next question would be: “Is the code public?” … but as far as I can see there is no source code available that one could inspect. That leaves us with the verdict not verifiable.
Do your own research!
Try out searching for "lost bitcoins", "stole my money" or "scammers" together with the wallet's name, even if you think the wallet is generally trustworthy. For all the bigger wallets you will find accusations. Make sure you understand why they were made and if you are comfortable with the provider's reaction.
If you find something we should include, you can create an issue or edit this analysis yourself and create a merge request for your changes.