About X Card
About X Twin Multi-Sig
How to use an X card?
Security & Technical Information
Advanced Technical and Security Information // Security
Advanced Technical and Security Information // Trust
Advanced Technical and Security Information // Assurance
Buying Process
Shipping, Delivery, & Refund

Learn About Hardware Wallet

About X Card

X Card is a highly secure hardware and cold wallet that is made to store any kind of digital assets/ cryptocurrency/ Bitcoin on the blockchain. With an NFC-enabled phone, you can verify your balance and extract your assets if you want to move them to another wallet.

It is guaranteed to never disclose the private key. Handing a Card over, is by nature, an off-chain payment transaction. One can sell it as a gift or use it to make a payment. Essentially, it is a secure, smart wallet for digital assets.

An X Card is a durable plastic card with only one element. This element is a secure chip that holds the funds and the private key. The chip has an NFC antenna that allows you to check the balance and transfer your funds with an NFC-enabled phone.

At the moment, the X Card supports the following cryptocurrencies:

Bitcoin (BTC) and Ethereum (ETH)

In order to optimize for user experience, we kept it simple:
Each X Card is fixed to a certain cryptocurrency and can hold one private key at a time.

You could get an X Card through our online store: https://www.shop.kardx.id or your preferred marketplace such as Tokopedia.

About X Twin Multi-Sig

Multisig or multi signature is a safety feature enabled by asymmetric cryptography which allows two keys, as stored safely and secretly in the secure element of each Card, to independently sign a transaction to send money from the same wallet address. With this layer of security, users can mitigate the risk of a single-key wallet.

If you purchase a set of two X Cards, each programmed to access the same Bitcoin wallet using a blockchain-native 1-of-2 multi signatory feature. Think of the second Card as your backup key.

The “X Tap” wallet acts as an interface to process transactions and requests signatures from your Cards’ secure element chips. The cardholder ensures their possession of the keys by tapping their Card on the phone.

If you lose one Card, you will be able to access your wallet with the second Card. X Tap App will request a 1-of-2 signatures to allow you to extract your funds. In order to protect your Card, you must set up a passcode in X Tap App.

Anyone who may find the lost Card would be prevented access because of the password protection. In this event, you must send the funds to a new X Card set to ensure the same level of protection in the future.

If both Cards are lost, you won’t be able to recover your funds.

At the moment, the X Card supports the following cryptocurrencies:

Bitcoin (BTC) and Ethereum (ETH)

In order to optimize for user experience, we kept it simple:
Each X Card is fixed to a certain cryptocurrency and can hold one private key at a time.

You could get an X Card through our online store: https://www.shop.kardx.id or your preferred marketplace such as Tokopedia.

How to use an X card?

An X Card allows you to:
● Check the validity of the Card and the assets it’s holding.
● Show the assets blockchain address.
● Extract (send) funds to other Tangem Cards or blockchain wallets.
● Pay with the Card (under development,with licensed and
local crypto exchange).

For Android devices:
Download KardX in the Google Play Store here.

Tap the X Card on your phone's NFC reader (tap the Card the same way you use your Google Pay) and you’ll automatically be redirected to the Google Play Store.

For iOS devices:
Download KardX in the App Store here.

If you have ever used Apple or Google Pay, you know exactly how to check the value of the X Card and the number of funds it’s holding.
You just need to open the KardX App (available on the Google Play store here, or the KardX App for iOS, available here) and tap the Card on the NFC scanner inside your phone.

Scanning the Card only takes a few seconds. The app will verify that the Card is genuine, ensure it possesses the correct private key, and obtain the balance from the blockchain. You can always double-check your balance directly in the blockchain explorer if needed. From this point, you can rest assured that you are the only holder of the private key and the funds on the Card.

Once the Card is scanned and verified, the app will display the exact blockchain address linked to the Card. You can use any other blockchain wallet app to transfer funds to the Card from a source wallet. You can also transfer funds from another Card using the KardX App.

To extract funds from an X Card, you will need an X Card, along with the KardX App on an NFC-enabled device.
Scan and verify the Card through the KardX App, then tap the ‘Extract’ button and prepare the outgoing transaction:

● Define the target wallet address
● Set the number of funds to transfer
● Accept the transfer fee

You will be asked to tap and hold the Card while it signs the transaction. In the end, the signed transaction will be broadcasted to the blockchain.

That’s all!

Please note: As the functionality of the NFC in the iOS 12 and below is limited to read-only, sending data is not allowed.
This means that you can only check the validity of the Card and any funds it’s holding.

You can load or extract them using iPhone models (from iPhone 7 & up) with iOS 13 or iOS 14.

The X Cards are fully reusable. There is no limit for transactions or for how many times you perform loading/ extraction operations.

The X Cards are limitless. You can send as many funds to your X Card as you want.
Before transferring a substantial amount of assets to self-custody, we recommend seeking professional advice regarding portfolio allocation and other saving practices.

We know it’s a little disappointing that you can only check the validity of the Card with your iPhone. But the functionality of our KardX App totally depends on the iOS NFC functionality. iOS 12 and below limits NFC functionality to read-only, so sending data is not allowed.

Security & Technical Information

Each X Card holds a secure chip that allows you to store and carry digital assets. The private key is generated by and permanently stored within the chip. Nobody has access to it either during or after the manufacturing process. This means that nobody ca

You can neither import the private key into an X Card nor export the private key -- so it’s completely impossible to have a copy. The architecture of each Card guarantees the chip inside is the only place in the universe where the unique key can ever be located.

The security of Tangem technology is audited by the Kudelski Group, a listed Swiss security company. The report is available here. After the audit, the chip firmware cannot be modified by KardX, or even by Tangem. Its intactness in each Card can be verified with the KardX App. The app and the NFC communication protocol are open sources.

Not to worry - nobody will be able to transfer funds from your Card just by scanning it. Although checking the funds takes seconds, transferring them requires you to hold the Card against your phone for 15-30 seconds.
This is a security measure, its duration is configurable and it can be overridden by enabling a PIN code on the Card (available on demand).

As with traditional banknotes, an X Card has to be kept physically secure at all times. The whole cryptocurrency value is always solely represented by the chip inside, hence cannot be accessed without the Card.
If you lose the X Card, you lose the assets. That’s why we don’t recommend loading a large number of funds onto the Card.

The electronics inside X Cards are designed to have incredible resilience against attacks and wear. On top of that, every single Card undergoes comprehensive testing during and after manufacturing.
Every time you validate an X Card, it checks the internal consistency. It will ask you to extract its value at the slightest suspicion of something going wrong.

While KardX and Tangem make no further warranties, you can mail your X Card to our offices around the world. If our labs are able to extract the value or determine that there was a loss of value due to an unknown manufacturing defect, we’ll work with you directly on a case-by-case basis.

As a company, KardX and Tangem is purely a hardware technology vendor and does not hold or operate any cryptocurrency. Loading assets in X Cards is done entirely by third parties like exchanges, wallets, custodial services, etc.

We know it’s a little disappointing that you can only check the validity of the Card with your iPhone. But the functionality of our KardX App totally depends on the iOS NFC functionality. iOS 12 and below limits NFC functionality to read-only, so sending data is not allowed.

Advanced Technical and Security Information // Security

An X Card has only one component inside — an ultra-secure chip that is tailor-made to protect digital assets. Unlike other hardware wallets, KardX does not use generic non-secure microelectronics that can be exploited to extract valuable data.

A wallet private key, which is the key to the ownership of blockchain assets, is always securely generated inside the X Card chip. The key cannot be injected from outside, backed up, or restored. Thus, the Card holds a unique and unclonable instance of the wallet.

A holder of an X Card doesn’t have to worry about the Card’s history or trust previous owners. Once the Blockchain is validated with the KardX mobile app, there is a 100% guarantee that the holder of the Card exclusively owns the corresponding Blockchain asset.

Each X Card stores a unique authentication key that can be verified with KardX and Tangem Authentication Service to make sure the Card is genuine and was manufactured by KardX and Tangem. This service is anonymous and optional KardX mobile apps will alert the user if the Card is unknown to KardX and Tangem.

The Card’s firmware is constant. The integrity of the whole Card’s binary code can be validated directly with the KardX mobile apps against a code footprint generated by an independent security auditor. This type of end-to-end code validation mechanism guarantees that no single Card has been tampered with and that no changes have been made, by KardX or even Tangem.

Every X Card can be protected with a user-defined password. Even without a password, the Card will effectively protect itself from drive-by attacks by requiring the user to hold the Card against the phone for a significant amount of time.
The NFC communication channel between the Card and the phone is encrypted and tamper- proof.

Advanced Technical and Security Information // Trust

Funds are always under the full control of the cardholder. KardX does not process incoming or outgoing transactions and does not operate its own trusted nodes. Our open-source mobile apps communicate directly with a random open Blockchain node to obtain a wallet balance and broadcast transactions. Advanced users can fine-tune nodes according to their preferences

Smart-card technology dictates a “security through obscurity” approach. Disclosure of the source code within secure elements would render hardware wallets vulnerable. In order to prove that KardX and Tangem firmware has no backdoors or bugs that would lead to loss of funds, Tangem has employed a renowned independent security auditor, Kudelski Security. The results of the audit are here:
https://research.kudelskisecurity.com/2018/08/06/audit-of-tangems-smartcard-wallet-code/amp/

KardX and Tangem firmware works on a native microcontroller level and does not rely on non-transparent platforms, such as third-party implementations of JavaCard VM. There are also no mechanisms to remotely control or update the firmware after the Card is manufactured.

Each X Card stores a unique authentication key that can be verified with KardX and Tangem Authentication Service to make sure the Card is genuine and was manufactured by KardX and Tangem. This service is anonymous and optional KardX mobile apps will alert the user if the Card is unknown to KardX and Tangem.

The Card’s firmware is constant. The integrity of the whole Card’s binary code can be validated directly with the KardX mobile apps against a code footprint generated by an independent security auditor. This type of end-to-end code validation mechanism guarantees that no single Card has been tampered with and that no changes have been made, by KardX or even Tangem.

Every X Card can be protected with a user-defined password. Even without a password, the Card will effectively protect itself from drive-by attacks by requiring the user to hold the Card against the phone for a significant amount of time.
The NFC communication channel between the Card and the phone is encrypted and tamper- proof.

Advanced Technical and Security Information // Assurance

Simple and durable Card construction: the chip is protected against impact and the environment by a solid hermetic package and three layers of plastic. The chip carries the most advanced protected flash memory, providing the maximum possible data retention time — up to 50 years at room temperature.

KardX and Tangem guarantee the compensation of lost funds if the loss was caused by a Card’s failure. Our compensation policy is described in the Terms & Conditions.

No Cards manufactured by KardX and Tangem depend on any special infrastructure, or on KardX and Tangem as a company. In an emergency situation — for example, if KardX Apps were removed from app stores — any trusted application supporting KardX and Tangem NFC protocols could be used to sign and broadcast transactions.

Buying Process

First, you should select the items you want to purchase. Click on the “Add to cart” button to add them to your basket. Use the shopping cart initially to collect articles you would like to order.
Click on “Shopping Basket” at the top of the page, at the right and you would like to view your products.
Once your selection is final, click on the “Checkout” button to start the order process.
Now follow the instructions and fill out your contact information and your preferred shipping address. On the right side, we will show you an overview of your order.
Next step: Click on the “Continue to shipping” button to choose a suitable shipping option for you.
Next: Click on the “Continue to Payment” button to choose a payment method. Available payment methods: > List of PM > List of PM > List of PM
To complete your order, click on the “Complete Order” button. By clicking on the button, you submit your order and we will process it soon.

Need more help?
Please contact us through help@kardx.id

To search for a specific product, simply enter your search term in the search field, and then confirm your query. Alternatively, you can find our full products here

No, you can order as many card as you would like to

You will automatically receive an e-mail confirmation once you have completed your order. It contains all the details of your order. We will send you again a confirmation as soon as we have fulfilled your products from our warehouse.

Yes, you can remove item from your shopping cart at any time, as long as you have not already sent the order. Simply click on “Shopping Basket” and remove the articles you no longer want.

Available payment methods at Checkout:

Redeem your voucher or discount code directly at the Checkout. Depending on the type of promotion, the relevant amount will be shown once you have entered your voucher code and then deducted from your order total, or the bonus product will be added to your shopping cart.

Shipping, Delivery, & Refund

Currently, we are only shipping in the Indonesia region only. However, we do have a plan to deliver within the Southeast Asian region.

Yes, we do offer free shipping for a select regions and under a limited timeframe.

We are currently in stock.
We will start the fulfillment once your order process is completed and typically finishes it by a day after the completion of order

checkout.
Once dispatched, an email will be sent containing the tracking number for the parcel

As soon as your order has left the warehouse, we will send you a notification with tracking information. It will be updated in 24 hours.
If you can’t find it, please write to us: help@kardx.id

Depending on the shipping destination, customs may apply. KardX Shop is not responsible for any customs and taxes that is applied to your order. All fees imposed during or after shipping are the responsibility of the customer (tariffs, taxes, etc).

To be eligible for a return, your item must be unused and in the same condition that you received it. It must also be in the original packaging.

To complete your return, we require a receipt or proof of purchase. Please do not send your to purchase back before further confirmation.

Notes: Please do understand that our App are currently under a development, you may or may not be able to full use the functionality of the App itself. This matter are not covered under the return or refund policy.

If applicable - Once your return is received and inspected, we will send you an email to notify you that we have received your returned item.

We will also notify you of the approval or rejection of your refund. If you are approved, then your refund will be processed, and a credit will automatically be applied to your credit card or original method of payment, within a certain amount of days.

Late or missing refunds (if applicable)

If you haven’t received a refund yet, first check your bank account again.

Then contact your credit card company, it may take some time before your refund is officially posted.

Next, contact your bank. There is often some processing time before a refund is posted.

If you’ve done all of this and you still have not received your refund

We only replace items if they are defective or damaged. If you need to exchange it for the same item, send us an email at help@kardx.id and send your item to:

To return your product, you should mail your product to:

[ADDRESS]

You will be responsible for paying for your own shipping costs for returning your item. Shipping costs are non-refundable. If you receive a refund, the cost of return shipping will be deducted from your refund.