TL;DR
What’s New in V2
Thank you to everyone who supported and provided feedback on the original proposal. The feedback was clear: while the core concept was well received, the solution needed native mobile wallet support and a simpler, mobile-first user experience.
Over the past few months, we evaluated several regulated card issuing platforms capable of supporting native Apple Wallet and Google Wallet provisioning. Following discussions with Rain, we identified its regulated Visa issuing platform as the right foundation for Version 2. Rain has since provided sandbox access and developer APIs, enabling us to validate the architecture and begin integration planning.
Based on community feedback, Version 2 introduces four key improvements:
• Tap-to-pay with Apple Wallet and Google Wallet. Users can add a virtual Visa card for seamless contactless payments.
• Mobile-first experience. The browser extension has been replaced with a streamlined payment flow.
• Regulated infrastructure. Card issuance, compliance, and Visa connectivity are provided through Rain’s regulated platform.
• Reduced funding request. The grant request has been reduced from $70,000 to $45,000 while preserving the project’s core deliverables.
The proposal maintains its original objective**: enabling CKB holders to spend directly from self-custody through existing global payment infrastructure.**
Executive Summary
CKB Anywhere Card V2 transforms CKB into a practical payment asset by allowing users to spend directly from self-custody anywhere Visa is accepted.
Users add a virtual Visa card to Apple Wallet or Google Wallet, enabling contactless payments at more than 175 million Visa-accepting merchants worldwide. Unlike traditional crypto card products, users retain full custody of their CKB until they explicitly authorize an individual purchase.
The payment architecture separates user authorization from card settlement. Before a purchase is completed, the user approves a one-time spending authorization by signing a smart contract transaction from their self-custody wallet. Anywhere Payment then settles the corresponding Visa transaction using a revolving liquidity facility, after which the authorization contract transfers the approved amount of CKB to replenish that settlement. By removing blockchain confirmation times from the checkout experience, the system delivers fast, familiar card payments while preserving user custody until each transaction is explicitly authorized.
Phase 1 integrates JoyID as the reference wallet implementation due to its mobile-first design, biometric passkey authentication, and seamless user experience. The underlying authorization framework is wallet-agnostic by design, allowing additional Nervos wallets to integrate without changes to the payment architecture.
Card issuance, Visa network connectivity, compliance, and native Apple Wallet and Google Wallet provisioning are provided through Rain’s regulated card infrastructure, enabling regulated card issuance across more than 150 jurisdictions and acceptance at over 175 million Visa merchant locations worldwide.
This proposal requests $45,000 USD (payable in CKB) to develop the authorization smart contract, complete platform integration, perform an independent security audit, and deliver a production-ready payment layer on Nervos mainnet within four months.
Rather than funding a standalone consumer application, this proposal delivers reusable payment infrastructure that any compatible Nervos wallet can integrate. By enabling direct spending of self-custodied CKB through existing global payment rails, it expands the real-world utility of the Nervos ecosystem while preserving decentralization, transparency, and user ownership.
The result is shared infrastructure that serves the broader ecosystem rather than a single application, allowing future wallets, developers, and payment experiences to build on the same open authorization framework without duplicating development effort.
1. The Problem
CKB is one of the most capable UTXO blockchains, yet spending it in everyday commerce remains difficult.
Today, CKB holders can acquire, store, and participate throughout the Nervos ecosystem, but spending those assets typically requires transferring funds to a custodial platform before making a purchase. This introduces unnecessary friction, reduces user control, and undermines one of cryptocurrency’s core principles: self-custody.
Most existing crypto card products rely on pre-funded custodial accounts or require users to convert assets before spending. While these approaches enable card payments, they require users to relinquish custody before a transaction occurs.
Other solutions attempt to settle blockchain transactions during payment authorization. Although technically feasible, introducing blockchain settlement into the payment path increases complexity and creates additional points of failure in a process users expect to complete within seconds.
At the same time, Apple Wallet and Google Wallet have become the standard interface for contactless payments across most major markets. Payment solutions that cannot integrate with these platforms introduce unnecessary friction and fall short of modern user expectations.
CKB Anywhere Card V2 addresses these challenges by combining:
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Self-custody. Users retain control of their CKB until they explicitly authorize each purchase.
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Familiar payments. Contactless payments anywhere Visa is accepted using Apple Wallet or Google Wallet.
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Regulated infrastructure. Card issuance, compliance, and Visa connectivity are provided through Rain’s regulated platform.
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Fast settlement. User authorization is separated from Visa settlement, eliminating blockchain confirmation times from the checkout experience.
Rather than introducing another custodial crypto card, CKB Anywhere Card V2 delivers reusable payment infrastructure that enables CKB to participate in everyday commerce while preserving the ownership principles of the Nervos ecosystem.
2. The Solution — Smart Contract Authorization & Revolving Settlement
CKB Anywhere Card V2 separates two functions that conventional crypto card products typically combine:
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User authorization
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Visa settlement
Rather than requiring users to preload funds into a custodial account or depending on real-time blockchain settlement during payment authorization, V2 introduces a Nervos-native authorization model supported by a revolving liquidity facility.
Before making a purchase, the user signs a one-time authorization through a compatible Nervos wallet. This authorizes a single transfer of the approved CKB amount within a short validity window while the assets remain under their control.
The user then completes payment by tapping their phone using Apple Wallet or Google Wallet. Rain processes the Visa authorization while Anywhere Payment settles the transaction using the revolving liquidity facility, allowing merchants to receive a standard Visa authorization without interacting with blockchain infrastructure.
Following payment authorization, the smart contract validates the signed approval and transfers the authorized amount of CKB from the user’s wallet to the replenishment account. Each authorization is single-use, time-limited, and limited to the exact amount approved by the user.
The temporary gap between Visa authorization and on-chain settlement is covered by the revolving liquidity facility. Settlement is continuously monitored, failed transfers are automatically retried, and new payment authorizations are paused if settlement cannot be completed within predefined operating thresholds.
To mitigate short-term market volatility, an exchange-rate snapshot is taken before the user authorizes the transaction. The smart contract calculates a maximum transferable CKB amount using this reference rate together with a predefined volatility buffer. If market movement exceeds the permitted tolerance before settlement is completed, the authorization automatically expires and the payment must be approved again.
By separating blockchain authorization from Visa settlement, CKB Anywhere Card V2 preserves self-custody while delivering the fast, familiar payment experience users expect from modern payment cards.
3. Architecture
Rain — Card Issuance & Visa Network Access
Anywhere Payment operates as the program manager on Rain’s regulated card infrastructure.
Rain provides:
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Visa network connectivity
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Virtual Visa card issuance
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Regulatory compliance
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End-user KYC
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Native Apple Wallet provisioning
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Native Google Wallet provisioning
This integration enables regulated Visa card issuance across more than 150 jurisdictions without requiring the Nervos ecosystem to build or operate traditional card issuing infrastructure.
Wallet Authorization Layer — JoyID (Phase 1)
Phase 1 integrates JoyID as the reference wallet implementation due to its mobile-first design, biometric passkey authentication, and seamless payment experience.
Before payment, the user signs a one-time smart contract authorization through JoyID. The signed authorization is valid only within a short authorization window and authorizes a single transfer of the approved CKB amount for the user’s next purchase.
The authorization framework is wallet-agnostic by design. Any Nervos wallet that implements the required authorization interface can integrate without changes to the underlying payment architecture.
Neither Anywhere Payment, Rain, nor any third party can initiate a transfer without the user’s explicit authorization.
Nervos Smart Contract
The authorization smart contract serves as the trust layer between the user’s wallet and Anywhere Payment’s settlement infrastructure.
For every payment, the smart contract:
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Validates the user’s signed authorization
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Verifies that the authorization has not expired
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Enforces single-use execution
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Calculates the approved CKB transfer amount
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Transfers only the amount authorized by the user to the replenishment account
Replay protection, expiry validation, and single-use execution ensure that every authorization can only be executed once.
Before mainnet deployment, the smart contract will undergo an independent third-party security audit, and the completed audit report will be published publicly.
4. Comparison
| Feature | Legacy Crypto Cards | CKB Anywhere Card V2 |
|---|---|---|
| Custody | Custodial / Pre-funded | Self-custodial — CKB remains in the user’s wallet until settlement is authorized |
| Funding Model | Manual deposits or top-ups | One-time wallet authorization |
| Payment Authorization | Assets transferred before spending | User authorizes each purchase through their wallet |
| Visa Settlement | Pre-funded by the user | Immediately settled through the revolving liquidity facility |
| Form Factor | Physical and virtual cards | Virtual Visa card in Apple Wallet and Google Wallet |
| Asset Location | Held by the card provider | Remains in the user’s wallet until settlement is authorized |
| User Experience | Deposit → Wait → Spend | Authorize → Tap → Done |
5. Transaction Flow
Step 1 — Authorize
The user opens a compatible Nervos wallet and authenticates using the wallet’s supported authorization method. In Phase 1, this is provided through JoyID using biometric passkey authentication.
The wallet generates a one-time authorization permitting a single smart contract execution within a short authorization window. No assets move during this step.
Step 2 — Tap to Pay
The user taps their phone using Apple Wallet or Google Wallet.
Rain processes the Visa authorization request while Anywhere Payment immediately settles the transaction using the revolving liquidity facility, allowing the merchant to receive a standard Visa authorization without interacting with blockchain infrastructure.
Step 3 — On-Chain Settlement
Immediately after payment authorization, the Nervos smart contract validates the signed authorization and transfers the approved CKB amount from the user’s wallet to the replenishment account.
Replay protection, expiry validation, and single-use execution ensure each authorization can only be executed once.
To protect against short-term market volatility, the authorization uses an exchange-rate snapshot taken before wallet approval together with a predefined volatility buffer. If market movement exceeds the permitted tolerance before settlement completes, the authorization automatically expires and the payment must be approved again.
Step 4 — Liquidity Replenishment
Accumulated CKB is periodically converted into USDC once predefined operating thresholds have been reached. The resulting USDC replenishes the revolving liquidity facility for future payments. Because this conversion occurs outside the payment authorization path, exchange execution has no impact on the user’s payment experience.
6. DAO-Owned Revolving Liquidity Facility
The proposal includes a $10,000 DAO-owned revolving liquidity facility that bridges the brief interval between Visa authorization and on-chain settlement.
Rather than being consumed as an operational expense, the facility continuously recycles as payments settle and liquidity is replenished, allowing the same capital to support future transaction volume.
Custody
The DAO-owned liquidity facility is held within Rain’s regulated payment infrastructure.
User CKB is never held by Anywhere Payment or Rain before settlement. Users retain full self-custody until they explicitly authorize each payment.
Replenishment
Following on-chain settlement, accumulated CKB is periodically converted into USDC through automated exchange execution once predefined operating thresholds have been reached. USDC serves solely as the operational settlement asset used to replenish the revolving liquidity facility, as Visa settlement requires a stable-value asset.
Transparency
All smart contract settlement transactions remain publicly verifiable on Nervos Layer 1.
Monthly operational reports will include:
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Liquidity balances
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Facility utilization
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Replenishment activity
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Transaction volume
These reports will be published to DAO stewards and the wider community.
Operational Controls
Settlement transactions are continuously monitored.
Temporary infrastructure failures are automatically retried. If settlement cannot be completed within defined operating parameters, new payment authorizations are paused until normal operation is restored.
DAO-appointed multi-signature stewards retain an emergency kill switch capable of disabling middleware access to the liquidity facility if activity falls outside approved operating parameters.
Settlement Failure & Liquidity Protection
Visa authorization and CKB settlement are separated by design. If a Visa payment is authorized but on-chain settlement cannot complete, the middleware automatically retries settlement and temporarily pauses new authorizations if failures exceed predefined operating thresholds.
The revolving settlement facility is protected through:
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Per-transaction spending limits
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Velocity controls
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Merchant risk controls
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One-time wallet authorizations
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Settlement monitoring
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DAO-controlled emergency pause mechanism
These controls limit exposure during settlement failures, prevent continued processing when settlement issues occur, and allow operations to be paused while issues are investigated and resolved.
Chargebacks & Risk Management
Chargebacks are handled through Visa’s standard dispute process.
Risk is managed through:
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Per-transaction spending limits
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User velocity controls
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Merchant risk controls
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One-time wallet authorizations
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Immediate on-chain settlement
This governance model ensures community capital remains transparent, recoverable, and protected by clearly defined operational controls while enabling practical real-world payments on Nervos.
7. Funding Request
| Component | Amount | Purpose |
|---|---|---|
| Revolving Liquidity Facility | $10,000 | DAO-owned revolving liquidity facility released following successful completion and community approval of Milestone 2. |
| Smart Contract Development & Independent Security Audit | $15,000 | Development of the authorization smart contract, wallet authorization logic, independent security audit, and security remediation. |
| Middleware & Platform Integration | $20,000 | Rain integration, wallet integration, Apple Wallet and Google Wallet provisioning, replenishment automation, compliance onboarding, testing, and production deployment. |
| Total Requested | $45,000 | Payable in CKB. |
The funding request has been reduced from the original proposal while preserving the project’s core deliverables.
Of the total request, $10,000 is allocated to a DAO-owned revolving liquidity facility that remains a community asset rather than a development expense. Excluding this facility, the development budget is $35,000.
The development funding will deliver a production-ready, audited payment layer, including the authorization smart contract, integration with regulated Visa infrastructure, and deployment on Nervos mainnet.
8. Delivery Milestones
Milestone 1 (Months 1–2) — Smart Contract & Platform Integration
Deliverables
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Authorization smart contract deployed to the Nervos testnet
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End-to-end payment authorization successfully demonstrated
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JoyID integrated as the Phase 1 reference wallet
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Rain API integration completed
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Apple Wallet and Google Wallet provisioning operational within the test environment
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Independent smart contract security audit commissioned
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Replenishment automation implemented and tested
Milestone 2 (Month 3) — Mainnet Launch
Deliverables
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Authorization smart contract deployed to Nervos mainnet
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Apple Wallet and Google Wallet provisioning available through Rain
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Independent security audit completed and published
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End-to-end payment flow publicly demonstrated
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Settlement transactions publicly verifiable on Nervos Layer 1
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Community verification of milestone completion
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Release of the DAO-owned revolving liquidity facility following milestone approval
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Monthly operational reporting begins
Milestone 3 (Month 4) — Operational Validation
Deliverables
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Early community onboarding
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Production monitoring and performance optimization
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Monthly operational reporting
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Technical documentation published
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Wallet-agnostic authorization framework prepared for future Nervos wallet integrations
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Architecture roadmap published outlining future evolution toward channel-based settlement through technologies such as the Fiber Network while preserving the existing wallet authorization framework
9. Why This Matters for Nervos
CKB Anywhere Card V2 extends the practical utility of CKB beyond storing and transferring value by enabling everyday payments without requiring users to surrender custody of their assets.
Rather than introducing another custodial crypto card, the project establishes reusable payment infrastructure built around Nervos’ native smart contract capabilities. It demonstrates how regulated payment infrastructure and decentralized asset ownership can work together while preserving the principles that define the Nervos ecosystem.
The architecture is designed for the ecosystem rather than a single wallet implementation. The platform is designed to evolve alongside the Nervos ecosystem. While payments initially settle directly on Nervos Layer 1, the architecture can incorporate future settlement technologies such as the Fiber Network without changing the wallet authorization model or user experience.
Benefits to the Nervos Ecosystem
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Real-world utility. CKB becomes spendable at more than 175 million Visa merchants through Apple Wallet and Google Wallet.
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Self-custody preserved. Users retain control of their assets until they explicitly authorize each payment.
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Fast payments. Payment authorization is separated from blockchain settlement, eliminating confirmation times from the checkout experience.
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Reusable infrastructure. The authorization framework can be adopted by future Nervos wallets and payment applications.
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Transparent governance. Settlement transactions remain publicly verifiable on Nervos Layer 1 and are supported by monthly operational reporting.
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Security-first architecture. The authorization smart contract will undergo an independent third-party security audit before mainnet deployment.
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Permanent community asset. The DAO-owned revolving liquidity facility continues supporting payment volume long after the grant has been completed.
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Future-ready design. The architecture can evolve alongside the Nervos ecosystem as additional settlement technologies mature.
Funding this proposal delivers foundational payment infrastructure that expands the practical utility of CKB, strengthens the Nervos ecosystem, and provides reusable infrastructure for future wallets and payment applications.
10. About Build Union & Anywhere Payment
Build Union is a multichain product development collective focused on building practical infrastructure that connects blockchain networks with real-world financial systems.
Anywhere Payment is Build Union’s payments platform, designed to enable self-custodial digital asset spending through regulated card infrastructure.
Website: https://anywherepayment.xyz/
Build Union has executed a mutual NDA with Rain and has been granted access to Rain’s developer sandbox and APIs for integration, testing, and technical validation throughout development.
Build Union Ltd is a registered company in the United Kingdom (Company No. 16676071).
Team:
The engineering team has experience developing payment card infrastructure, directly relevant to the card issuing, settlement, and authorization components required for this system. Build Union has also previously built within the Nervos ecosystem.
Emmanuel (Nervos Talk: BuildUnion) https://www.linkedin.com/in/emmanuelstreetcredit/
Has led business development and product initiatives across multiple blockchain ecosystems, including Nervos, with a focus on connecting decentralized infrastructure to practical financial applications.
A seasoned blockchain architect specializing in smart contracts, DeFi, and NFT solutions. Successfully led the development of UTXO and ERC-20 token ecosystems and consulted on blockchain infrastructure projects requiring advanced cryptocurrency and distributed systems expertise. His experience includes designing custom smart contracts, deploying DeFi architectures, and delivering fintech products at scale.
Sergey Chekriy https://github.com/sergey-chekriy
A full-stack and blockchain developer with more than 15 years of experience building end-to-end products. He has architected and launched complex Web3 applications, including Thrust.com, and contributed to the architecture of major DeFi platforms such as Seedify.fund. His expertise spans secure smart contract development, scalable Web3 infrastructure, and AI-powered applications.
Laxman https://www.linkedin.com/in/trylaxman/
A full-stack and blockchain developer with over 15 years of experience in end-to-end product development. Has architected and launched complex Web3 applications like Thrust.com and contributed to the architecture of prominent DeFi platforms like Seedify.fund. Specializes in secure Web3 systems, smart contract development, and AI integrations, focusing on scalability and maintainability.
Closing
CKB Anywhere Card V2 transforms CKB from an asset that can be stored and transferred into one that can be spent through the world’s existing payment infrastructure while preserving self-custody. Rather than funding a wallet-specific application, the Nervos DAO is investing in reusable payment infrastructure that any compatible wallet can integrate. This creates lasting ecosystem value by expanding the utility of CKB, lowering the barrier for future wallet integrations, and establishing an open foundation for real-world payments on Nervos.