Review 39 – CoolWallet


I’m always on the lookout for competition in the Bitcoin ecosystem. I’m a firm believer that competition breeds innovation and keeps prices down. Don’t get me wrong, I think there’s definitely something good about being an established name with a proven track record. It fosters trust and respect. However, I’ve seen far too often that trust and respect turn into a weapon to use against the customer. Companies have been known to adopt a “we know best; trust us” attitude, a disdain for the customer’s needs and wants, a general ignorance of support issues, and setting price points because “we can; they’ll pay it”.

Take Bitcoin hardware wallets, for instance. If you ask around about them you’re most likely to be given one of two names. Both of these companies are well established and have a long, proven, track record. I have nothing bad to say about either of them. However, one product, aside from software updates, really hasn’t changed since it appeared on the scene. The other has several products at several price points, but they certainly don’t fit every use case. So, I’m always on the lookout for alternatives. I found several on the market and reached out to them. I offered to do reviews in exchange for a model with which to review. The first one to take me up on the offer was CoolWallet from CoolBitX Technology.

Full Disclosure: I was contacted by the Co-Founder and COO of CoolBitX Technology, Michael Ou, and given a CoolWallet for free in exchange for writing this review. It could be implied that I got paid to write it, but I assure you that it will not affect my review.

coolwallet_01CoolWallet, as stated above, is a Bitcoin hardware wallet to be used for cold storage and transaction verification. Their claim is that it’s the “ultimate bitcoin wallet” and that it’s the “most convenient Bitcoin hardware wallet”. It is the size of a credit/debit card, fits in your wallet, uses Bluetooth Low Energy (BLE) or Near Field Communication (NFC) to communicate. It has an e-paper screen for a display. There are plenty of security features that I will cover as well. It works with phones, tablets, or computers using an associated software wallet (iOS, Android, and Windows for now, but Linux and Mac are being developed).

Under the hood, CoolWallet uses a Secure Element chip to store Bitcoin private keys. Your keys never leave the device. It also has a One Time Password (OTP) generator, meaning you can have 2FA enabled for transactions. The BLE and NFC connections, as well as the charging cradle being an NFC reader as well, mean that nearly any device can connect to it, provided they finish the Linux and Mac software. The e-paper display is roughly 1” by 1” (24.6mm x 21.9mm to be exact), the contrast is comfortable even in the sun, and the viewing angle is rather wide. It’s durable: pressure resistant, bendable up to 15 degrees, and waterproof. There is also a 12 month warranty on the device. The connections and screen are very low power and the battery last a long time. Coupled with the auto-sleep, I was able to write this review, constantly turning the device on and off after leaving it on my dresser for a week for a test. The battery is still full.

coolwallet_02My first impression was that the box is really slick looking. The gold on black is really bold and I like it.

coolwallet_03Open the box and the CoolWallet is prominently displayed.

coolwallet_04The charging cradle is underneath. It has a sticker on it to show the correct way to charge the CoolWallet. Under the sticker is a lightning bolt. Personally, this seems like a missed opportunity to display another logo, but you can’t mistake what the cradle is for.

coolwallet_05Also in the box are a brief instruction manual, a recovery card, and a short USB to micro USB cable.

coolwallet_06The front of the CoolWallet looks really cool. The e-paper screen is in the upper left. Below that, the only button is clearly labeled with a circle. On the right is a prominent logo. At the bottom is the name of the device and their slogan.

coolwallet_07The back of the CoolWallet is vaguely credit/debit card-like, but without getting too close. The upper left has the serial number and the upper right has the batch number. Underneath all this in the middle is a QR code that links to the website. I’m assuming the white space is a place to write the name you’ve given the card. We’ll get to that later. On the right indicates the location of the button on the front. This one, however, has the circle around the Bitcoin symbol. It kind of makes me wish they’d done the same on the front.

coolwallet_08Holding the CoolWallet button for a few seconds turned on the device. It greeted me with a Hello and then immediately requested that I launch the app.

coolwallet_09As I’m an Android user, I went to the Play Store and installed the app.

coolwallet_10Upon opening the app, it looked pretty stark, but that’s ok.

coolwallet_11It soon began searching for a CoolWallet with which to pair.

coolwallet_12And when it found one, that’s when the fun began.

coolwallet_13Clicking connect brought up an OTP verification screen.

coolwallet_14I simply punched in the OTP number displayed on the CoolWallet and told it to pair with this phone.

coolwallet_15It took a moment to pair the devices.

coolwallet_16It then told me when pairing is successful.

coolwallet_17Note here that it mentions that you can pair the CoolWallet with up to three devices.

coolwallet_18I was then given the option to create a new wallet or restore an old wallet. I wasn’t brave enough to attempt importing another of my HD seeds, so I settled for creating a new wallet.

coolwallet_19Then the CoolWallet switches to Config Seed mode. You can either select to have the seed generated in the CoolWallet itself by selecting a seed generated by sets of numbers or you can choose to have the seed generated in the app by selecting a seed generated by a list of words.

coolwallet_20If you choose to generate your seed in the CoolWallet you select Card (numbers) and choose either 8, 12, or 16 numbers to be used to generate the seed.

coolwallet_21The CoolWallet will then display a series of numbers. You write down the first one, click the button, write down the second number, and so forth until you’ve written down the amount of numbers you chose to create your seed above. Note: It was here that I noticed that generating a seed with 12 or 16 numbers does not work. The CoolWallet will only display 8 of the numbers, which invalidates the checksum verification. I’ll get to that later on. Just know that 8 is your only valid option and it does work.

coolwallet_22If you choose to generate your seed in the app you select App (words) and choose either 12, 18, or 24 words to be used to generate the seed. If you don’t like the list of words you’re given you can click on the slider bar and it will give you an alternate set of words.

It should be noted that choosing numbers is probably more secure as the seed is then generated on the CoolWallet card, along with all the keys, but choosing words allows you to recover your seed using other HD wallet software if a problem arises.

coolwallet_23In either case it will take a moment to generate the seed.

coolwallet_24If you chose numbers the app will ask you to add up all the numbers you’re given and punch in the sum to validate that you’ve written down your backup correctly. Note: per the note above you now see how missing numbers will affect the outcome and invalidate the checksum.

coolwallet_25If you chose words the app will ask you to verify several words displayed to validate that you’ve written down your backup correctly.

coolwallet_26If you’ve done either correctly you’ll see the screen switch to say it’s syncing.

coolwallet_27Once this is complete, you end up with a blank software wallet in the app.

Speaking of the software app, it’s a little barebones for my taste but this should not detract from CoolWallet. It’s meant to be simple and easy to use. It does everything it needs to do and it does it very well. It sends and receives bitcoin. It allows you to set up transactions and request bitcoin. It shows you a list of transactions. As software wallet apps go, it does the job. Then consider how it does it with the hardware wallet and I’m sold. Let’s take a closer look.

coolwallet_28Because I’m a sucker for settings and getting things situated before I start using them let’s first look at the menu and options.

coolwallet_29In the Host Devices section you can see to which devices this particular CoolWallet is linked. You can link each CoolWallet hardware wallet to up to three devices. Your phone, your computer, and your tablet, for instance. It should be noted that, if your computer does not come with NFC or BLE compatibility, you can use the charging cradle and USB cable to connect it to a computer. I thought that was pretty cool.

coolwallet_30In the CoolWallet Card section you can change the name of the card. Names are limited to 8 characters. As I mentioned above, it might come in handy if you have multiple CoolWallets to name them and write the name in the white space on the back. Or you could always just go with the serial number. Also in this section you can switch the CoolWallet to display the fiat value instead of the BTC value, but who would want to do that? I should note here that, although each CoolWallet can only pair with three devices, the software wallet on your devices can pair with any number of CoolWallets.

coolwallet_31In the Security section you can toggle various security features. You can enable OTP for transactions, meaning you would always have to have the card with you to punch in the OTP code displayed on the card in order to send bitcoin. You could turn off the need to press the button on the card to complete transactions, but that’s one step shy of just using a software wallet. You can enable the watchdog function, which will tell the software wallet to notify you if the hardware wallet gets too far from your phone. You can also turn on an option to show the sending address on the card, if you need that for some reason.

coolwallet_32In the deceptively named Settings section you’ll find a list of fiat currencies to set the exchange value of your BTC balances.

coolwallet_33Logout does exactly what you think it does.

coolwallet_27Let’s go back to the Home area. As you can see at the top there is 1 HD wallet. It includes a balance and a fiat value in the currency I’ve chosen. This applies to only this HD wallet.

coolwallet_34As you can see on the CoolWallet there is one HD wallet in the hardware wallet and it matches the software wallet.

coolwallet_35If you were to press the plus on the software wallet or swipe left it will create a second HD wallet.

coolwallet_36As you can see on the CoolWallet there is now a second HD wallet in both the software wallet and the hardware wallet. Each CoolWallet can have up to 5 HD wallets.

coolwallet_37In the Receive part of the wallet you can see that each wallet will display up to 4 addresses you can use to receive bitcoin. You can also label the addresses if you plan to use them for something specific, request a payment of a specific amount, and then copy the address to the clipboard of your device. As you use them they will be replaced. Remember that each HD wallet can have nearly a limitless amount of addresses.

coolwallet_38As you can see, I’ve received some bitcoin and my CoolWallet is displaying a balance in both BTC and fiat on the home screen. And it now shows a transaction list under the balance.

coolwallet_39If we look at the CoolWallet, the card is showing the same.


Clicking on the transaction in the list shows the details of the transaction. Further details can be seen by clicking on the View At button at the bottom.

coolwallet_41In the Sending section you can see that it’s just as simple. You can enter an address or use the camera to scan a barcode. You then enter either a BTC amount or a fiat amount which will then be converted automatically.

coolwallet_42Once you’re ready you hit Send. But this is where having a hardware wallet is nice. If you left the option on to require a button press to confirm transactions you’ll need to hit the button on the CoolWallet to confirm the transaction. If you turned on the option to require an OTP code to confirm transactions you’ll need to enter the security code displayed on the card to confirm the transaction.

coolwallet_43And sent…

So, what’s wrong with it? At the end of my reviews I always go over what I don’t like about a product. And there’s always something that doesn’t work for me.

I have a couple simple gripes that could be fixed with software updates, like the misnamed “settings” section of the menu or the fact that choosing numbers to generate a seed only works with 8. Another is the time I tried to spend unconfirmed coins from the transaction where I had just sent bitcoin to the CoolWallet. Instead of telling me that I couldn’t do that because the bitcoin was not yet confirmed the app just crashed. I understand how Bitcoin works and I know I’m not supposed to do that, but an error message would be so much better than a crash. I also have seen issues where refreshes to update data stall and I have to restart the app to clear them up. This generally works, but could be fixed as well. (In speaking with CoolBitX Technology, they’ve confirmed that all of these will be corrected with a software update.

Aside from that, being a Linux guy, I’d really like to see the Linux software released. (CoolBitX Technology tells me that this will require more resources and much more demand from Linux users. So, if you want this as bad as I do, let them know.)

I was rather surprised at finding out that CoolWallet is not open source. But upon reading the FAQ it looks like they plan on opening the source for their micro controller unit code and firmware on the card. They also plan to open source their software wallet code. The secure element, understandably, will not be open source, however they are open to having a respected member or members of the Bitcoin ecosystem or security industry to audit said code and verify that it’s trustworthy. I can live with this arrangement. But until it’s done, I wouldn’t trust a fortune to it. (CoolBitX Technology did correct me slightly here and point out that their iOS and Android apps are on GitHub.)

A matter of inconvenience, I feel, was was that after creating a set of 5 HD wallets in the software wallet and sync them to the card, those are the ones you get. No more, no less. Unfortunately it does not appear that you can delete just one wallet, number four for instance, and create a new one. You can’t even archive and hide them to get another to replace them. So, if you use a main one and then use the other four for something like a project or budget scheme, once you decide to stop using them you’re stuck moving all your bitcoin somewhere else, resetting the CoolWallet with another seed, and then using the new HD wallets it creates. Again, this is a bit of an inconvenience, but it’s doable.

I’m not a big fan of single points of failure, either. I’d like to see it changed to offer more options for exchanges and transaction information. There are several exchanges for the USD rate, for instance, but I can’t choose which one I generally watch, or even which one the CoolWallet uses. As for transaction data, I don’t want to talk bad about a product that has done so much good for Bitcoin, but what happens if goes down? They’ve had problems in the fairly recent past, so it’s not outside the realm of possibility. From where will my CoolWallet get updates?

coolwallet_44Something I feel that is a much larger issue is that there’s no security locking down the CoolWallet screen. Anyone can pick it up and know exactly how much bitcoin I have stored on it. Here it is charging and you can see my balance. I would rather see it require a connection to the phone, at least as an option. Again, from reading the FAQ, I know the plan is to allow transactions using NFC without the mobile device present, but I really don’t like it that someone can see the contents just by turning it on.

The last problem I have, and the one that I have absolutely no tolerance for, is that the hardware wallet matches the software wallet except in one respect: The balance on the CoolWallet is in uBTC, or microbitcoin. Remember back in my earlier tutorial where I discussed conversions? This is one you’ll have to get used to because, unfortunately, this is not an option that can be changed. And, also unfortunately, if your balance gets large enough, it switches over to mBTC, or millibitcoin. Again, this is not an option that can be changed. If I were to pick one failure spot for CoolWallet it would be this. I understand that the card itself has a limited display. However, the software wallet does not. At least make the two match. (CoolBitX Technology assured me that this is going to change so that the app matches the card. This may require a firmware update, which they will provide instructions for if needed. They did not say whether we would get to set the denomination, but it’s a step in the right direction to match up. It’ll remove some confusion.)

But even then, I really do like the CoolWallet as a device. I like the form factor and connection options better than the Trezor. It’s got a display and more connection options than a Ledger Unplugged. It’s half the price and thinner than a Ledger Blue or Case. It uses a simple push button and OTP instead of fingerprints. All the keys are under my control instead of multi-sig. It’s lightweight, durable, and an all around great device. I plan on keeping and using mine in the same way I used to use the Ledger Uplugged: as a device to put in my wallet to secure balances larger than pocket money. I had to give up my Ledger Unplugged when I bought a phone with no NFC. I would also like to see a service where they custom print them. I would be ecstatic to be able to buy one with my website logo on the front, for instance.

My final verdict is that I’m very happy I discovered the CoolWallet and would recommend it to anyone looking for a midrange Bitcoin hardware wallet. Pick one up for yourself today at CoolBitX Technology.

Posted in Desktop, Hardware, Mobile, Reviews, Wallets

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