X150-Valkyrie: Offline, one-touch & Hydra L2 payments

[Proposal setup] Proposal title

Please provide your proposal title

X150-Valkyrie: Offline, one-touch & Hydra L2 payments

[Proposal Summary] Budget Information

Enter the amount of funding you are requesting in ADA

100000

[Proposal Summary] Time

Please specify how many months you expect your project to last

12

[Proposal Summary] Translation Information

Please indicate if your proposal has been auto-translated

No

Original Language

en

[Proposal Summary] Problem Statement

What is the problem you want to solve?

Cardano users face mnemonic attack risks, high L1 fees for micro-payments, and the inability to transact without an internet connection (offline).

[Proposal Summary] Supporting Documentation

Supporting links

• https://docs.google.com/document/d/1Z0i5Yp2EgDUwlRRj_beY2sCM6Y9zhhSOk3x4IdOT-Go/edit?usp=sharing

[Proposal Summary] Project Dependencies

Does your project have any dependencies on other organizations, technical or otherwise?

No

Describe any dependencies or write 'No dependencies'

No dependencies

[Proposal Summary] Project Open Source

Will your project's outputs be fully open source?

Yes

Please provide details on the intellectual property (IP) status of your project outputs, including whether they will be released as open source or retained under another licence.

The entire mobile application code for Android will be made public on GitHub under the MIT license, including all services, UI components, and utility functions. This ensures transparency, allows the community to conduct independent security audits, and encourages other developers to contribute or build upon the product, strengthening the entire ecosystem.

[Theme Selection] Theme

Please choose the most relevant theme and tag related to the outcomes of your proposal

Wallet

[Campaign Category] Category Questions

Describe what makes your idea innovative compared to what has been previously launched in the market (whether by you or others).

X150-Valkyrie introduces three innovations to the Cardano mobile landscape that have not been combined before:

• Mobile Hydra layer 2: Unlike existing server-focused implementations, we bring a Hydra light client directly to Android, enabling instant, near-zero fee micro-transactions for retail users.
• True offline payments: We utilize Bluetooth Low Energy (BLE) to allow "air-gapped" transaction signing, enabling payments even without an internet connection a first for Cardano mobile wallets.
• Mnemonic attack resistance: We implement a proprietary 24-to-36 word encryption standard that protects user funds even if their physical backup is exposed.

Describe what your prototype or MVP will demonstrate, and where it can be accessed.

To ensure security and stability, development will strictly follow a testnet-first approach on Cardano pre-prod, culminating in a mainnet release by the project's end. The final Android MVP (APK available on GitHub) will demonstrate:

1. Hydra lifecycle: The ability to open a head, perform instant off-chain swaps, and settlement back to layer 1.
2. Offline payments: Signing a transaction in "airplane mode" and broadcasting it via BLE to a recipient device.
3. One-touch interaction: Initiating a secure transaction flow via NFC. Community members can access the source code and APK releases on our public GitHub to verify these on-chain activities.

Describe realistic measures of success, ideally with on-chain metrics.

We focus on realistic, verifiable on-chain metrics for the first 12 months of development and initial launch:

1. Active users: Onboarding 70+ active mainnet wallets within the first 3 months of the public release.
2. Transaction volume: Executing 500+ successful transactions (combined layer 1 payments and layer 2 Hydra snapshots).
3. Scalability testing: Successfully opening and closing 50+ Hydra heads on-chain, proving mobile L2 viability.
4. Developer impact: Achieving 30+ GitHub forks and 150+ stars, indicating that other developers are using our open-source SDKs for Hydra and BLE.

[Your Project and Solution] Solution

Please describe your proposed solution and how it addresses the problem

In the broader blockchain ecosystem and Cardano in particular mobile wallets are a critical tool for users to store, manage, and transact assets. However, current solutions force users to choose between convenience and security, with no real solution that balances both. This leads to four major problem areas:

1. Security limitations
   1. Exposure of private keys and mnemonics: Most mobile wallets require users to record their recovery phrases (mnemonics) in raw form. In practice, many users store mnemonics by taking screenshots, writing notes in memo apps, or saving them in unencrypted files. This exposes assets to theft if the device or data is compromised.
   2. Lack of multi-layered security: Many wallets do not support biometric authentication or advanced attack-resistant mechanisms, leaving asset protection dependent on a single layer of security.
2. No offline transaction signing (air-gapped)
   1. Current wallets cannot perform offline transactions, making it difficult for users to pay directly at stores or transact nearby in poor or no internet conditions. Transactions cannot be completed instantly, causing inconvenience for both buyers and sellers.
3. Cumbersome payment process
   1. To initiate a transaction, users must manually input the recipient address and token amount. This manual process leads to poor user experience and risks errors such as sending tokens to the wrong address.
4. Scalability & micro-transaction fees (the Hydra necessity)
   1. High L1 fees: For micro-payments (e.g., buying a coffee, bus ticket), the standard layer 1 fee is disproportionately high relative to the item value.
   2. Latency: The ~20-second block confirmation time on layer 1 is not ideal for instant retail experiences that require "swipe-and-go" speed.

Consequences for users and ecosystem

• New users: Prone to mistakes in mnemonic storage, leading to irreversible asset loss.
• Cardano ecosystem: Slows user adoption and limits advanced use cases like secure offline payments or instant retail payments making Cardano less competitive compared to other blockchain networks.

Introducing X150-Valkyrie

These limitations have driven us to develop X150-Valkyrie an advanced wallet that adds offline capabilities, Hydra layer 2 scaling, one-touch payments, and high-level security.

1. Optimized security: Mnemonic attack resistance
   1. We use a proprietary 24→36 mnemonic security mechanism (Password-Locked).
      1. Mechanism: Valkyrie transforms the original 24-word seed into a 36-word encrypted mnemonic. It encodes entropy with a password-derived keystream and separates the encrypted 24-word entropy from a 12-word salt.
      2. Security: Only the 36-word mnemonic is displayed/stored; the original seed never exists on the device in raw form and can only be recovered with the correct password.
      3. Encryption standard: Data is encrypted using AES-256-CBC with PBKDF2 (100k iterations), virtually eliminating mnemonic exposure risk even if the user saves the words insecurely.
2. Offline payment (air-gapped signing)
   1. X150-Valkyrie allows users to create and sign transactions entirely offline.
      1. BLE transmission: Signed data is transmitted to the seller’s device via Bluetooth Low Energy (BLE).
      2. Data integrity: Transactions are chunked with integrity checks (CRC, ACK/RESEND) to ensure data is not corrupted during transmission.
      3. Queueing: Transactions are queued securely and automatically broadcast to the blockchain once the recipient's device connects to the internet.
      4. Fallback: QR codes are provided as a fallback when BLE is limited.
3. One-touch payment (NFC)
   1. Users can pay ADA with a single tap.
      1. Process: After unlocking via biometric authentication, the device uses an integrated NFC chip. When brought near an NFC reader/phone, the transaction is automatically initiated.
      2. Hardware security: We utilize the smartphone's built-in Secure Enclave/TEE to protect private keys during this process, ensuring that the keys never leave the secure hardware environment.
4. Hydra layer 2 integration (instant & low cost)
   1. To solve the scalability issue, X150-Valkyrie integrates a Hydra node light client directly into the mobile app architecture.
      1. Isomorphic state channels: Users can open a "Hydra head" (a secure state channel) with frequent partners or merchants directly from the app.
      2. Instant finality: Transactions inside the head happen off-chain with near-instant confirmation (< 1 second).
      3. Near-zero fees: Making micro-transactions (buying coffee, paying for parking) economically viable on Cardano.
      4. Settlement: Users can close the head at any time to settle the final state back to the layer 1 blockchain securely.
5. Advanced user center
   1. DeFi & staking dashboard: Manage staking and interact with DeFi protocols.
   2. Transaction alerts & analysis: Integrates WhaleTrack to monitor whale wallet activity.
   3. AI stake pool performance tracker: A simple AI tool to analyze data and suggest pools based on user priorities (maximizing returns or decentralization).

Development strategy

To build a truly complete product that delivers optimal performance and security, the project will undergo multiple complex development phases.

• Phase 1 – Core foundation: We will focus on deploying the essential components first to ensure stability: Core wallet management, mnemonic encryption, biometric authentication, and basic layer 1 transaction handling.
  

• Phase 2 – Connectivity & scaling: Building upon the stable core, we will integrate the advanced modules: Offline payments (BLE/QR) and the Hydra layer 2 client. This phased approach ensures that complex features like Hydra and NFC are built on a secure and tested foundation.

[Your Project and Solution] Impact

Please define the positive impact your project will have on the wider Cardano community

X150-Valkyrie will deliver clear and measurable value

1. Pioneering mobile scalability with Hydra (layer 2): Currently, Hydra is mostly a tool for developers or specific server-side applications. X150-Valkyrie will be one of the first mobile wallets to bring Hydra head technology directly to end-users. By enabling instant, near-zero fee micro-transactions on mobile, we demonstrate that Cardano is ready for high-frequency retail use cases (e.g., buying coffee, paying for transport), significantly reducing the load on layer 1.
2. Bridging the gap to real-world payments: By implementing offline payments (BLE) and one-touch (NFC), we remove the technical barriers that prevent crypto from being used in daily life. This opens up Cardano adoption in regions with unstable internet connectivity and provides a user experience comparable to Apple Pay or Google Pay, but in a decentralized manner.
3. Elevating mobile security standards: We address the critical vulnerability of mnemonic storage. By offering mnemonic attack resistance (24→36 word encryption) and hardware-backed security for free, we protect new users from irreversible asset loss due to human error.
4. Open source infrastructure: The entire project, including the complex logic for Hydra client integration on Android and BLE/NFC communication, will be open-source. This serves as a valuable reference implementation for other developers, saving them months of R&D time and accelerating the overall ecosystem development.

Sharing results with the community

We are committed to full transparency and will share outputs via:

1. GitHub: The full source code (MIT License) and the compiled APK files will be hosted here.
2. Demo videos: High-quality videos demonstrating the "Offline payment" flow and "Hydra instant settlement" in real-world scenarios.
3. Technical documentation: A dedicated documentation site for developers wishing to fork our code or learn about mobile Hydra integration.
4. Project reports: Monthly progress reports and a final close-out report and video submitted to the Catalyst community.
5. Community channels: Active engagement on Cardano Forum, Twitter/X, and technical Discord channels to gather feedback and support users.

[Your Project and Solution] Capabilities & Feasibility

What is your capability to deliver your project with high levels of trust and accountability? How do you intend to validate if your approach is feasible?

We are a group of developers with practical experience in mobile security, Android system architecture, and blockchain development. We started building on Cardano in early 2024 and have won the Cardano Vietnam Hackathon in both 2024 and 2025.

Our team combines two main skill sets. Some of us have spent years in mobile application development, focusing on low-level protocols like Bluetooth (BLE) and NFC for secure data transmission. Others come from a Web3 background, specializing in Hydra layer 2 scaling and cryptographic security. This mix allows us to build a wallet that bridges the gap between complex blockchain technology and seamless everyday user experience.

We focus on solving real-world adoption barriers specifically connectivity limits (offline payments) and scalability (micro-transactions) rather than just building another standard wallet interface. Our goal is simple: to provide a secure, "always-ready" payment tool that brings the convenience of modern fintech to the decentralized world. X150-Valkyrie is the solution built to address these specific needs.

[Milestones] Project Milestones

Milestone Title

Design & initialization

Milestone Outputs

• Market research:
  • Survey on current payment methods in crypto
  • Survey on payment experience outside crypto (real-world)
  • Survey on user needs & behavior
  • Survey on barriers & opportunities for application
• Technical requirements document: Functional & non-functional requirements
• System architecture design
• UI/UX design (Android app)
• Public GitHub initialization: README, contribution guidelines, MIT license

Acceptance Criteria

• Completed survey report covering all 4 research areas listed in outputs
• System architecture diagram clearly describing system components, data flow, and relationships
• Technical requirements document including:
  • Functional requirements for the system
  • Non-functional requirements such as security, performance, scalability
• UI/UX design for the Android app, including all interface components and user flows covering both core features and advanced features of the wallet
• Public GitHub repository initialized with README, contribution guidelines, and MIT license

Evidence of Completion

• Link to survey report (PDF)
• Link to system architecture diagram
• Link to technical requirements document (PDF)
• Link to Figma file containing UI/UX design of the application
• Link to public GitHub repository containing MIT License, README, and contribution guidelines

Delivery Month

2

Cost

10000

Progress

20 %

Milestone Title

Core development phase 1 (Key management & security, transaction management)

Milestone Outputs

• Key management & security development: Create/restore wallet, encrypt mnemonic from 24 to 36 words, biometric authentication, auto-lock
• Transaction management development: Send/receive tokens, UTXO handling, fee estimation, transaction signing, address verification, transaction history
• Unit testing: Full unit tests for each feature
• UI development: User interface for the above two features

Acceptance Criteria

• Key management & security module developed with stable functionality on testnet: wallet creation/restoration, mnemonic encryption with attack resistance mechanism, biometric authentication, and auto-lock
• Transaction basic management module developed with successful functionality on testnet: send/receive tokens, UTXO handling, fee estimation, transaction signing, address verification
• 100% unit test cases executed successfully
• Android interface fully supports all features described in the core key management & security and transaction management outputs

Evidence of Completion

• Link to GitHub commit containing complete source code of the modules
• Test report (PDF) showing 100% test case pass rate
• Link to public demo video showcasing the features of the modules described in the output

Delivery Month

5

Cost

28000

Progress

50 %

Milestone Title

Core development phase 2 (Assets management + staking + Hydra integration)

Milestone Outputs

• Assets management development: Display balances & values, manage tokens/NFTs.
• Staking management development: Delegate to pools, track rewards, withdraw rewards, undelegate.
• Hydra integration (basic): Implement basic Hydra client logic to support opening a head, committing funds, and closing a head on testnet.
• Unit testing: Full unit tests for each feature.
• UI development: User interface for the above three features.

Acceptance Criteria

• Assets management developed with support for displaying asset balances and values, syncing data directly from the blockchain, converting to fiat (USD, EUR, VND…), and managing tokens and NFTs with detailed views of token quantities and NFT collections
• Staking management developed with successful functionality on testnet: delegation to pools, reward tracking, reward withdrawal, undelegation
• 100% unit test cases executed successfully
• Hydra integration: Successfully demonstrate the ability to initialize a Hydra head connection and perform a basic state transfer (snapshot) on the testnet environment within the app logic.
• Android interface fully supports features described in assets management, staking, and Hydra outputs.

Evidence of Completion

• Link to GitHub commit containing complete source code of the modules
• Test report (PDF) showing 100% test case pass rate
• Link to public demo video showcasing the features of the modules described in the assets management, staking management outputs and Hydra head initialization.

Delivery Month

8

Cost

17000

Progress

80 %

Milestone Title

Advanced development (Offline payment, one-tap payment)

Milestone Outputs

• Offline payment module development: Create & sign transactions offline, transmit data via Bluetooth, set up secure queue in wallet, auto-send when internet is available, add QR code fallback option
• One-tap payment module development: NFC payment with one touch, biometric authentication before payment, transaction processing & encryption according to Cardano standards
• Unit testing: Full unit tests for each feature
• UI development: User interface for both modules

Acceptance Criteria

• Offline payment module developed with successful functionality on testnet: create & sign transactions offline, transmit data via Bluetooth, set up secure queue in wallet, auto-send when internet is available, QR code fallback option
• One-tap payment module developed with successful functionality on testnet: NFC payment with one touch, biometric authentication before payment, transaction processing & encryption according to Cardano standards
• 100% unit test cases executed successfully
• Android interface fully supports all features described in the offline payment and one-tap payment outputs

Evidence of Completion

• Link to GitHub commit containing complete source code of the modules
• Test report (PDF) showing 100% test case pass rate
• Link to public demo video showcasing the features of the two modules described in the output

Delivery Month

11

Cost

30000

Progress

90 %

Milestone Title

System integration & Android release on mainnet

Milestone Outputs

• Integrate 4 modules (Core wallet & security, transaction basic management, offline payment, one-tap payment) into a complete Android application
• Perform integration testing and system testing with end-to-end scenarios covering features of all 4 modules
• Deploy public demo APK on mainnet for community installation.
• Conduct user survey on product feature experience and collect feedback for improvement
• Improve product based on feedback
• Write user guide (PDF)
• Close-out report
• Close-out video

Acceptance Criteria

• Android application fully integrates all modules and runs stably on Cardano mainnet
• All end-to-end scenarios tested successfully on Android devices
• Interface meets minimum consistency standards (Material Design) and is user-friendly
• Demo APK installable and usable by community testers
• Minimum of 50 users surveyed for product feature experience and feedback collected
• Product improved based on feedback
• Clear user guide document with demo video
• Close-out report includes content as required by the community
• Close-out video includes content as required by the community

Evidence of Completion

• Link to GitHub repository containing fully integrated source code of all modules
• Test report (PDF) of end-to-end scenarios
• Link to public demo APK file
• Link to Google Sheet containing list of feedback from test users
• Product improvement report based on feedback
• Demo video of full usage flow
• User guide (PDF)
• Link to public close-out report
• Link to public close-out video

Delivery Month

12

Cost

15000

Progress

100 %

[Final Pitch] Budget & Costs

Please provide a cost breakdown of the proposed work and resources

The budget is allocated based on engineering effort (estimated at ~45-50 ADA/hour for mobile/blockchain engineers) and essential project overheads.

1. Design & initialization (10,000 ADA): ~215 hours. Allocated for market research, defining the technical architecture for the Android environment, and creating the UI/UX designs.
   1. Tasks:
      1. UI/UX design (Android app): (4,000 ₳)
      2. Market research: (2,000 ₳)
      3. Develop system architecture design document: (2,000 ₳)
      4. Technical requirements document (Functional & non-functional): (2,000 ₳)
      5. Initialize public GitHub (README, MIT license): (0 ₳)
2. Core development phase 1 (28,000 ADA): ~580 hours. This phase focuses on the foundational security layers (mnemonic encryption, biometrics) and basic transaction handling logic.
   1. Tasks:
      1. Mnemonic encryption with attack resistance & security: (3,900 ₳)
      2. Fee estimation, Tx signing & address verification: (3,400 ₳)
      3. UTXO handling & coin selection: (3,400 ₳)
      4. Create/Recover wallet logic: (2,600 ₳)
      5. Send/Receive tokens logic: (2,200 ₳)
      6. Biometric authentication: (2,000 ₳)
      7. Store & sync transaction history: (1,600 ₳)
      8. Auto-lock & session policy: (1,000 ₳)
      9. Develop user interface for core features: (3,800 ₳)
      10. Full unit testing: (3,600 ₳)
      11. Testnet integration & demo video: (500 ₳)
3. Core development phase 2 (17,000 ADA): ~340 hours. Focused on integrating the Hydra client, asset management, and staking operations.
   1. Tasks:
      1. Hydra integration: (3,840 ₳)
      2. Stake pool delegation & management: (1,320 ₳)
      3. Reward tracking & withdrawal: (2,580 ₳)
      4. Display balance & fiat conversion: (1,360 ₳)
      5. Blockchain data synchronization: (1,190 ₳)
      6. Token management: (1,190 ₳)
      7. Undelegation logic: (680 ₳)
      8. Develop user interface for assets/staking: (2,040 ₳)
      9. Full unit testing: (2,300 ₳)
      10. Testnet integration & demo video: (500 ₳)
4. Advanced feature development (30,000 ADA): ~600 hours. Developing the "offline" and "one-tap" capabilities, including BLE data transmission and NFC handling.
   1. Tasks:
      1. Develop user interface for advanced features: (4,200 ₳)
      2. One-tap NFC (tap-to-pay) logic: (4,000 ₳)
      3. Tx handling & encryption (Cardano standards): (3,600 ₳)
      4. Data transfer via Bluetooth (BLE): (3,300 ₳)
      5. Create & sign offline transactions: (3,000 ₳)
      6. Secure queue & retry mechanism: (2,400 ₳)
      7. Auto-send when internet is available: (2,100 ₳)
      8. Biometric authentication (One-tap): (1,800 ₳)
      9. QR code fallback method: (1,500 ₳)
      10. Full unit testing: (3,600 ₳)
      11. Testnet integration & demo video: (500 ₳)
5. System integration & Android release (15,000 ADA): ~280 hours. Covers server costs, final end-to-end testing, community feedback loops, and documentation.
   1. Tasks:
      1. Operational costs, server & API service: (4,200 ₳)
      2. Integration & system testing (end-to-end): (3,290 ₳)
      3. Implement product improvements based on feedback: (2,397 ₳)
      4. Deploy public demo APK on testnet: (1,658 ₳)
      5. Conduct user survey & collect feedback: (1,658 ₳)
      6. Write user guide documentation: (1,348 ₳)
      7. Close out report + video: (449 ₳)

Detail budget: https://docs.google.com/spreadsheets/d/1zNOgHm9twebEavBy13bTI4Ine6q5u_y4I6c_VTMx-PM/edit?usp=sharing

[Final Pitch] Value for Money

How does the cost of the project represent value for the Cardano ecosystem?

The project creates foundational public infrastructure. A free, open-source, high-security mobile wallet will elevate Cardano’s value for all users. The majority of the cost is allocated to security auditing, directly protecting the community’s assets. With a small investment, the community receives a complete, audited product that can prevent millions of USD in potential losses, raising the security standards and credibility of the ecosystem.

The proposed budget for the project is entirely reasonable when placed in the context of current labor market conditions and blockchain software development costs. Building a secure, open-source, and free mobile wallet for the community requires a team of engineers with extensive experience in blockchain, security, and infrastructure. The proposed cost has been carefully calculated to reflect market realities, ensuring it is sufficient to attract and retain high-quality personnel, while remaining within the average range compared to similar Web3 projects.

Importantly, the majority of the budget is allocated directly to security auditing and infrastructure operations two key factors in protecting user assets. This cost is not only technical but also a strategic investment to prevent risks that could result in millions of USD in losses for the community if a security incident occurs. Prioritizing the budget for auditing demonstrates the project’s commitment to placing user safety and trust at the forefront.

With a relatively small investment compared to the potential value the project delivers, the community will receive a complete product, professionally audited, accessible to all users, and fully open-source for community verification, contribution, and expansion. This project not only provides a practical tool for safer and more convenient Cardano usage, but also raises the overall security standards and reputation of the entire ecosystem.

The funds granted by the community are used transparently, reasonably, and deliver tremendous value not only by creating an immediately useful product for users, but also by reinforcing trust, minimizing risk, and ensuring the long-term sustainable growth of Cardano.

[Self-Assessment] Self-Assessment Checklist

I confirm that evidence of prior research, whitepaper, design, or proof-of-concept is provided.

Yes

I confirm that the proposal includes ecosystem research and uses the findings to either (a) justify its uniqueness over existing solutions or (b) demonstrate the value of its novel approach.

Yes

I confirm that the proposal demonstrates technical capability via verifiable in-house talent or a confirmed development partner (GitHub, LinkedIn, portfolio, etc.)

Yes

I confirm that the proposer and all team members are in good standing with prior Catalyst projects.

Yes

I confirm that the proposal clearly defines the problem and the value of the on-chain utility.

Yes

I confirm that the primary goal of the proposal is a working prototype deployed on at least a Cardano testnet.

Yes

I confirm that the proposal outlines a credible and clear technical plan and architecture.

Yes

I confirm that the budget and timeline (≤ 12 months) are realistic for the proposed work.

Yes

I confirm that the proposal includes a community engagement and feedback plan to amplify prototype adoption with the Cardano ecosystem.

Yes

I confirm that the budget is for future development only; excludes retroactive funding, incentives, giveaways, re-granting, or sub-treasuries.

Yes

[Required Acknowledgements] Consent & Confirmation

I Agree

Yes