Coldcard

[hZti]

It is not special in a way that I think everyone should be using it, but it is special in a way that it is much better than other hardware wallets that are using NFC. The other wallets are created 100 % on the smartphone and then loaded on the NFC chip. Coldcard is created 100 % on the coldcard hardware and only the transaction is send.

If I understand correctly, all hardware wallets need to have NFC chip built inside them, so Coldcard is not different from them in some special way.

The thing is that many NFC wallets are only basically and smartphone app and a card that has a writable NFC chip in it. So all the wallet management is done on the smartphone (creating the seed, signing transaction etc.): Basically the NFC chip is only a more fancy way to store a password. With coldcard this is different since all the wallet management is done offline and then sent via NFC to the smartphone.

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[n0nce]

The thing is that many NFC wallets are only basically and smartphone app and a card that has a writable NFC chip in it. So all the wallet management is done on the smartphone (creating the seed, signing transaction etc.): Basically the NFC chip is only a more fancy way to store a password. With coldcard this is different since all the wallet management is done offline and then sent via NFC to the smartphone.

Honestly, that doesn't mean ColdCard is exceptionally good; it just means the other NFC wallets are exceptionally bad. It's absolutely unacceptable for any hardware wallet to create the seed on a mobile phone.
Especially since ColdCard mk1-3 already existed, which all (correctly) created the seed on-device, it shouldn't be surprising or a novelty / security feature / selling point that they continue to do so. This should be one of the core essential aspects of a hardware wallet.
An argument such as 'other hardware wallets with NFC technology are super terrible' doesn't make the ColdCard a great product. You really shouldn't compare your product to the bottom-of-the-barrel ones as a means of marketing, that's not a good look.

[ranochigo]

If I understand correctly, all hardware wallets need to have NFC chip built inside them, so Coldcard is not different from them in some special way.
You need to have two devices with NFC chips that can communicate with antennas between each other, first device is smartphone with NFC chip, and second device is hardware wallet with NFC chip.
Good thing would be to make some comparison review and see how all NFC wallets work in real life scenarios.

Most hardware wallets don't have NFC chips. They are only necessary for wireless transfers, AFAIK both Trezor and Ledger doesn't have it. The cards that you see are not hardware wallets, and IIRC Ledger was about to launch one but the cards weren't very useful as the chips require too much power for NFC.

NFC is just another way of transferring data, so nothing really revolutionary or surprising.

[dkbit98]

The thing is that many NFC wallets are only basically and smartphone app and a card that has a writable NFC chip in it. So all the wallet management is done on the smartphone (creating the seed, signing transaction etc.): Basically the NFC chip is only a more fancy way to store a password. With coldcard this is different since all the wallet management is done offline and then sent via NFC to the smartphone.

None of other hardware wallets are online, so that is not really an argument if favor of Coldcard, and we still don't know how or if NFC even work in ColdCard.
I can also just use some old junk smartphone with nfc, remove my sim card, disable or remove antenna and wi-fi and I am getting offline device that can be used for offline wallet management, and sent to my other smartphone.
We all know that ALL previous Coldcard hardware wallets were hacked or exploited, so I see no reason why Mk4 should be any different, even if NKV said it's only exotic and rear exploits.
NFC is just one more extra attack vector.

Ledger was about to launch one but the cards weren't very useful as the chips require too much power for NFC.

Yes, they only need to add NFC chip, so they can officially receive reward for most circus-clown-like hardware wallit in the world  

[hZti]

Yes it is quiete disappointing that NVK is in this forum and apparently reads also this topic but doesn’t take the time to reply to the really important questions. Also they seem timbale some good support employees on Reddit but they also do not reply here and in general they don’t go into the more deeper technical details that we talk about.

[dkbit98]

Yes it is quiete disappointing that NVK is in this forum and apparently reads also this topic but doesn’t take the time to reply to the really important questions. Also they seem timbale some good support employees on Reddit but they also do not reply here and in general they don’t go into the more deeper technical details that we talk about.

Well I guess NVK is busy and bitcointalk forum is not high on his priority task list, but look what some new Coldcard Mk4 owners are reporting with their devices.
THeir reddit channel is not very much active and I think they are posting most things related with Coldcard wallet and other devices on their Twitter channel @COLDCARDwallet.
This is not the first time we see people received mk4 broken  factory defect devices that needs to be replaced with new one.

[DireWolfM14]

The thing is that many NFC wallets are only basically and smartphone app and a card that has a writable NFC chip in it. So all the wallet management is done on the smartphone (creating the seed, signing transaction etc.): Basically the NFC chip is only a more fancy way to store a password. With coldcard this is different since all the wallet management is done offline and then sent via NFC to the smartphone.

Honestly, that doesn't mean ColdCard is exceptionally good; it just means the other NFC wallets are exceptionally bad. It's absolutely unacceptable for any hardware wallet to create the seed on a mobile phone.
Especially since ColdCard mk1-3 already existed, which all (correctly) created the seed on-device, it shouldn't be surprising or a novelty / security feature / selling point that they continue to do so. This should be one of the core essential aspects of a hardware wallet.
An argument such as 'other hardware wallets with NFC technology are super terrible' doesn't make the ColdCard a great product. You really shouldn't compare your product to the bottom-of-the-barrel ones as a means of marketing, that's not a good look.

Unless I'm missing something, the NFC feature on the ColdCard is only used to send (and possibly receive) files to the mobile device.  For example you can create a wallet on your ColdCard, generate a wallet file for use with a desktop client such as Electrum, then you can send that file to your phone using NFC.  

I haven't gotten to the point of creating any transactions in my Mk4 just yet, but I assume you can use NFC to send and receive P/SBTs.  My unlocked Galaxy S21 is the global version which came with no bloatware installed.  It doesn't have an NFC file transfer app integral to the OS (that I now of) and I'm reluctant to install a third party app for the purpose.  I couldn't find a Samsung app, nor a Google app that does what I would need.

[hZti]

I couldn't find a Samsung app, nor a Google app that does what I would need.

Yes that is the same for iOS. So far the NFC feature is not usable since the software for mobile devices is missing. We can only hope that they implement a NFC feature maybe in Bluewallet or others.

I haven't gotten to the point of creating any transactions in my Mk4 just yet, but I assume you can use NFC to send and receive P/SBTs.  

You can pretty much send/recive anything from the CC that you otherwise would transfer via MicroSD card like public keys, PTBs etc.

Yes it is quiete disappointing that NVK is in this forum and apparently reads also this topic but doesn’t take the time to reply to the really important questions. Also they seem timbale some good support employees on Reddit but they also do not reply here and in general they don’t go into the more deeper technical details that we talk about.

Well I guess NVK is busy and bitcointalk forum is not high on his priority task list, but look what some new Coldcard Mk4 owners are reporting with their devices.
THeir reddit channel is not very much active and I think they are posting most things related with Coldcard wallet and other devices on their Twitter channel @COLDCARDwallet.
This is not the first time we see people received mk4 broken  factory defect devices that needs to be replaced with new one.

Is it known if you could fix it by replacing the screen so it could be a DIY or is also the controller broken?

[n0nce]

Unless I'm missing something, the NFC feature on the ColdCard is only used to send (and possibly receive) files to the mobile device.

Yes, that's correct; you will be able to use NFC to transfer PSBTs between the ColdCard and your phone. As long as there is a mobile app for that; which it doesn't.

[DireWolfM14]

As long as there is a mobile app for that; which it doesn't.

Yeah, my phone isn't setup to receive or send data by default, and like I said previously I'm reluctant to using a third party app to transfer files between the wallet and my phone.  Maybe ColdCard is ahead of the curve, and we'll see some mobile wallet apps implement NFC file transfer capability in the near future.  But again, unless it's wallet app that I trust (like Electrum and... well, Electrum) I probably won't be using it at all.

[dkbit98]

I haven't gotten to the point of creating any transactions in my Mk4 just yet, but I assume you can use NFC to send and receive P/SBTs.  My unlocked Galaxy S21 is the global version which came with no bloatware installed.  It doesn't have an NFC file transfer app integral to the OS (that I now of) and I'm reluctant to install a third party app for the purpose.  I couldn't find a Samsung app, nor a Google app that does what I would need.

Is there a Bitcoin testnet option available for Coldcard, like there is for Trezor and some other hardware wallets?
It would be interesting to test NFC transactions without paying any actual fees, that is if you have some testnet coins

Note that BTC Sessions just released full video tutorial for new Coldcard Mk4 wallet, but I think he is basically their promoter for some time:
https://www.youtube.com/watch?v=FAYmE5-40PQ

Is it known if you could fix it by replacing the screen so it could be a DIY or is also the controller broken?

You can't fix this with display replacement, and you would probably void your warranty by opening it to do this, but good thing is that I heard Coldcard is accepting this as factory defect and they are replacing them with new devices.

[hZti]

Is it known if you could fix it by replacing the screen so it could be a DIY or is also the controller broken?

You can't fix this with display replacement, and you would probably void your warranty by opening it to do this, but good thing is that I heard Coldcard is accepting this as factory defect and they are replacing them with new devices.

I know that it is the more easy way to just ask for a replacement unit from coinkite directly. But in my opinion this could be a fault that would affect many more cold cards after maybe a few month or years of usage and then you would need to buy a completely new Coldcard again. Also maybe they are not even manufactured anymore. So for that reason I would hope to be able to replace parts myself.

[DireWolfM14]

Is there a Bitcoin testnet option available for Coldcard, like there is for Trezor and some other hardware wallets?

I just want to correct what I had written about the ColdCard and testnet; there is indeed a testnet mode.  Since the ColdCard doesn't sign transactions via USB, it must be in Testnet mode to create a wallet to export.

There's no specific setting on the ColdCard that puts the device in TestNet mode, or anything like that.  Like the Trezor, TestNet is handled on the client side.  I can use any of the compatible clients (i.e. Electrum, Wasabi...) to create a testnet wallet which requires the HW wallet to sign transactions.

[dkbit98]

I just want to correct what I had written about the ColdCard and testnet; there is indeed a testnet mode.  Since the ColdCard doesn't sign transactions via USB, it must be in Testnet mode to create a wallet to export.

I wonder why I can't find anything about that testnet functionality anywhere on Coldcard website FAQ page or documentation:/
I looked everywhere on internet and only thing I could find is few words mentioned on their website saying that XTN is testnet.
Theer are some mentiones about this in their github issues, and that's it.

EDIT:
Maybe this is connected with previous isolation bypass bug from 2020 that could be exploited using fake testnet transactions:


https://benma.github.io/2020/11/24/coldcard-isolation-bypass.html

[DireWolfM14]

I just want to correct what I had written about the ColdCard and testnet; there is indeed a testnet mode.  Since the ColdCard doesn't sign transactions via USB, it must be in Testnet mode to create a wallet to export.

I wonder why I can't find anything about that testnet functionality anywhere on Coldcard website FAQ page or documentation:/
I looked everywhere on internet and only thing I could find is few words mentioned on their website saying that XTN is testnet.
Theer are some mentiones about this in their github issues, and that's it.

EDIT:
Maybe this is connected with previous isolation bypass bug from 2020 that could be exploited using fake testnet transactions:


https://benma.github.io/2020/11/24/coldcard-isolation-bypass.html

I've found the documentation to be a bit misleading in some circumstances.  There seems to be some that's still pertaining to the Mk3 or possibly older wallets, and some has been updated to relate to the Mk4.  As for testnet on the Mk4, from the main menu you select Advanced>Danger Zone>TestNet, and their you'll find three options "Bitcoin" (which is mainnet,) "TestNet" and "RegTest."  I played around with Testnet a little bit this past weekend, and worked as I expected.

I tried to trick it, but I can't sign Testnet transactions unless the device is set to Testnet mode.  I've played with hardware wallets and Testnet before, and I was sure I had done so with my Trezors, but I realized it was in one of my old KeepKey seeds that I had all my tesnet coins locked up.  I fired up my old KeepKey (which works much like the Trezor) and confirmed it doesn't have a specific testnet mode.  You just need to pair it with an Electrum testnet wallet and from there everything works as one would expect.

[hZti]

Do you know how the testnet mode does actually work? Does it create a new seed that is shown to you or does it create a testnet wallet based on your normal seed? If I select testnet it seems that nothing happens to my device 

[dkbit98]

I've found the documentation to be a bit misleading in some circumstances.  There seems to be some that's still pertaining to the Mk3 or possibly older wallets, and some has been updated to relate to the Mk4.

I would say that Coldcard documentation is probably outdated, and they need to have separate page for mk4, especially if it has new functions like NFC.
Someone could argue that NFC is currently unusable, so they can add more information later down the road.

I tried to trick it, but I can't sign Testnet transactions unless the device is set to Testnet mode.

Well they obviously fixed that bug from 2020

I've played with hardware wallets and Testnet before, and I was sure I had done so with my Trezors, but I realized it was in one of my old KeepKey seeds that I had all my tesnet coins locked up.  I fired up my old KeepKey (which works much like the Trezor) and confirmed it doesn't have a specific testnet mode.

I think that even ledger and Trezor hardware wallets support testnet.
You can add this to ledger with separate app and in trezor just by enabling testnet in Trezor Suite.

[DireWolfM14]

Do you know how the testnet mode does actually work?

I've used it to create, sign, send, and receive transactions from a test-net wallet, so I do know that it does indeed work.

Does it create a new seed that is shown to you or does it create a testnet wallet based on your normal seed?

No, it doesn't need to create a new seed, it'll create a test-net wallet with whatever seed you have loaded in your ColdCard.  It's worth noting that any Bip39 passphrases you load in your ColdCard will generate new test-net wallets, just like the ColdCard would for main-net.

If I select testnet it seems that nothing happens to my device  

Other than the checkmark indicating that your ColdCard is in test-net mode, there won't be any changes to the device.  It functions just like it would normally.  To use test-net you'll need to export a wallet for the preferred client you want to use.  I use Electrum, so I exported an Electrum wallet from the ColdCard, and used Electrum Testnet client.  You must use the test-net client, Electrum's main-net client will not open a test-net wallet file, you'll get a warning.

On Windows go to Start Menu> Electrum> Electrum Testnet.  

On Linux, the easiest way (in my opinion) is to start it from the command line:

Code:

$ electrum --testnet

I would say that Coldcard documentation is probably outdated, and they need to have separate page for mk4, especially if it has new functions like NFC.

Agreed, the documentation does in fact seem outdated.  Many of the scrolling screen gifs show options/screens that I don't see on my Mk4.  It would be nice to have a separate documentation section for the different versions just to eliminate any ambiguity.  

I think that even ledger and Trezor hardware wallets support testnet.
You can add this to ledger with separate app and in trezor just by enabling testnet in Trezor Suite.

I don't know about Ledger, but the Trezor works just like the KeepKey.  There's no specific setting on the hardware itself that sets the device into test-net mode, it all happens on the client side.  I played with this a bit yesterday, and I was able to just plug in my Trezor, start up Electrum Testnet, and the Trezor paired up and I was able to create a new test-net wallet.  I didn't make any transactions, but I suspect it would work just like it does on main-net.

[hZti]

If I select testnet it seems that nothing happens to my device  

Other than the checkmark indicating that your ColdCard is in test-net mode, there won't be any changes to the device.  It functions just like it would normally.  To use test-net you'll need to export a wallet for the preferred client you want to use.  I use Electrum, so I exported an Electrum wallet from the ColdCard, and used Electrum Testnet client.  You must use the test-net client, Electrum's main-net client will not open a test-net wallet file, you'll get a warning.

Thank you I had the time to try it again and it indeed worked this time. I think the first time I simply didn't correctly choose testnet. Now that everything works I will try some stuff with multisig which is very nice implemented if you have access to more than one ColdCard.

[DireWolfM14]

Thank you I had the time to try it again and it indeed worked this time. I think the first time I simply didn't correctly choose testnet. Now that everything works I will try some stuff with multisig which is very nice implemented if you have access to more than one ColdCard.

You don't need a second ColdCard to play with multi-sig, you can have one signer from on the ColdCard and the other on a desktop wallet or a different brand of hardware wallet. 

Have you had a chance to play with the Bip85 seed generator?  That's a pretty darn cool feature, and perfect for secondary seed phrases.  I didn't even know about that bip until I got my ColdCard and started researching the implementation of that feature.