Unikeys showcases the first card based cryptocurrency transaction on top of payment channels

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Unikeys, a Hong Kong company dedicated to designing and providing biometric hardware wallet solutions, has successfully completed the development of a card based payment framework that enable instant cryptocurrency transactions in Ether. Enuma Technologies, a Hong Kong based blockchain development team has worked in partnership with Unikeys to utilise Sprites State Channels and Ethereum in order to enable instant payments without having to commit each individual transaction to the blockchain.

Off-chain transactions and the creation of payment channels between parties represent a highly reliable option for blockchain scalability. Sprites State Channels and other implementations like Connext or Lightning Network allow users to make nearly instantaneous transactions through off-chain payment channels. Payment channel transactions can be executed for extremely low fees, which enables cryptocurrencies like Ether or Bitcoin to be highly efficient payment means for small-value transactions.

The user experience around payment channels is already representing a serious challenge since an efficient implementation must allow consumers, merchants and enterprises to easily and seamlessly interact within networks of channels to perform high frequency transactions.

For the pilot, an Ether transaction was performed using Sprites State Channels. The working pilot relies on an Android app and a UKey biometric card hardware wallet that secures and facilitates signing of the transaction.

The company posted a video demonstration of the payment on YouTube.

Video demonstration of the payment channel on YouTube


The setup of the Unikeys payment channels architecture is as follows:

• To establish a connection to the payment channels infrastructure, a payment channel is funded through a transaction.

• The user has been issued a card and goes to a merchant to purchase goods.

• The card already has a payment channel setup with a payment provider, in this case Unikeys, and the merchant also has a payment channel with the same provider, Unikeys.

• Once the user authenticates using the UKey card, the card gets the transaction hash value through NFC.

• The card emits a unique signature through NFC.

• The payment and settlement are completed instantly.

To initiate payments with merchants, the consumer authenticates with the UKey card. In this example the consumer sends a payment to the Merchant via the off-chain payment channel. Each payment consists of two off-chain transfers, one between the consumer and Unikeys and one between Unikeys and the Merchant. When the consumer wants to send a payment, a random nonce (preimage) is generated and the key on the consumer’s UKey card is used to sign a Sprites message {amount, recipient, expiry, preimageHash} which is sent to Unikeys Payment Processor Backend. The backend also sends a Sprites message to the merchant. At that point, the consumer reveals the preimage, which unlocks both payments: from the consumer to Unikeys and from Unikeys to the merchant. Thanks to the atomicity guarantee of payment channels, the customer’s wallet will only get charged when the Merchant receives the money, and therefore Unikeys does not incur any risk by facilitating these payments.

The UKey card is the world’s first biometric-secured crypto wallet and allows consumers to store and use multiple cryptocurrencies in the simplest and most secure way. The pre-sale campaign for the UKey card was launched in May 2019. The UKey card enables holders to store and trade in cryptocurrencies including Bitcoin, Ether, Bitcoin Cash, Litecoin, Ripple and ERC20 Tokens backed by biometrics-based security.

The unique utilisation of Biometrics facilitate and highly secure access to private keys. Only Wallet holders can access the assets by pressing their finger on their cards in order to validate all mobile wallet transactions that are also encrypted using secure channel protocols. The two fingerprints and the private keys never leave the card and remain safe into the EAL6+ Secure Element. The frictionless user experience introduced by the UKey card removes the needs for relying on pincodes, and allow payments from both contact (EMV chip) and contactless (NFC) modes. Here is a link to the website: https://unikeys.io/.


The Unikeys and Enuma teams believe that the adoption of such networks will have a significant impact on the public approach towards cryptocurrencies. Decreasing the congestion of blockchain networks could remove one of the main burdens for a mainstream cryptocurrency adoption and offer the possibility to instantly exchange and send cryptocurrencies to merchants in everyday life, almost without a fee.

Alexandre Tabbakh, CEO and co-founder at Unikeys, states that more emphasis should be placed on “facilitating people’s ability to spend cryptocurrencies in our daily lives”, adding:

“Every one of us into the cryptocurrency community should participate and coordinate actions to come up with the most optimized and complete implementation for wider scalability. In order to make a contribution, we decided at Unikeys to have a particular focus on testing and developing solutions that have the ability to democratize the utilization of payments channels. “

Lionello Lunesu, CTO of Enuma Technologies, explains why the utilisation of payment channels is important and how it can solve some of the biggest challenges the blockchain ecosystem is facing:

“By leveraging state channels, users and merchants can immediately trust a crypto payment without having to transfer funds on-chain and waiting for blockchain confirmations.”

The objective of the pilot is to showcase the ability we have to provide real mainstream and secure cryptocurrency payments solutions. In order to offer a better payment experience, we not only need to create robust architectures but also solve the UX puzzle. At the end of the chain there are individuals that want convenience and security.

If you would like to get more details about the UKey card and the payment channels use case, feel free to get in touch with us at info@unikeys.io

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