AirGap Cold Wallet Solution x Zcash

Community Grants Applications
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Context

We plan to integrate Zcash to AirGap cold wallet solution enabling both shielded and non-shielded Zcash transactions. With AirGap users will be able to turn their spare device into a cold wallet. With AirGap’s additional security features, Zcash users can get a full-fledged secure, truly air-gapped cold wallet setup at home.

Detailed proposal - GitHub

Project Summary

AirGap is an open-source, air-gapped wallet solution with a unique two-app approach: AirGap Vault for offline transaction signing and AirGap Wallet for transaction creation and management. This setup transforms any spare smartphone into a secure cold wallet, offering robust security without the need for dedicated hardware.

Project Description

AirGap is a self-custody open source cold wallet that transforms any spare smartphone into an air-gapped cold wallet, providing maximum security without the need for dedicated hardware wallets. It consists of two applications:

- AirGap Vault (offline) – Stores private keys completely offline and signs transactions securely via QR codes, preventing any exposure to online threats.
- AirGap Wallet (online) – Manages balances, initiates transactions, and interacts with dApps, ensuring a seamless user experience.

AirGap introduction video

But why us?

True Randomness for Seed Generation – Unlike traditional wallets that rely on a device’s RNG (which can be manipulated), AirGap supports dice roll and coin flip entropy to generate seed phrases, ensuring verifiable, human-generated randomness for maximum security.

Totally Air-gapped Security – AirGap Vault operates without Bluetooth, USB cables, Wi-Fi, or NFC, making it 100% offline, eliminating any potential attack vector from connected devices.

Advanced Security features - AirGap includes BIP-39 passphrase protection, BIP-85 deterministic seed derivation, and social recovery, allowing users to add extra layers of security and flexibility to their wallets.

Experience with shielded protocols: Our team did implement shielded Sapling transactions for Tezos in AirGap Wallet. We have the skills, experience and knowledge to tackle this integration.

AirGap Presentation - General pitch deck.pdf

Proposed Problem

Zcash currently faces multiple challenges related to secure wallet storage and accessibility:

- Limited Hardware Wallet Options: Zcash users only have Trezor as a hardware wallet option. However, Trezor is not available in all regions, limiting its adoption.
- Supply Chain Vulnerabilities: Hardware wallets like Trezor are susceptible to supply chain attacks, where compromised devices can be tampered with before reaching the end user.
- Lack of Universally Accessible Cold Storage: Many users cannot access secure cold storage solutions due to geographic or financial barriers.
- Absence of User-Generated Entropy: Current Zcash wallets rely entirely on hardware-generated RNG (Random Number Generator) chips, which can be a single point of failure. They do not incorporate user-generated entropy, such as dice rolls or coin flips, which enhance randomness and security.
- Connectivity Risks in Existing Wallets: Most wallets rely on USB or Bluetooth connections, which can introduce attack vectors. A fully air-gapped solution would eliminate this risk.

Proposed Solution

AirGap provides a highly secure, universally accessible, and open-source alternative to traditional hardware wallets for Zcash users. It addresses the identified challenges through the following solutions:

1. Expanding Access to Secure Cold Storage

- Hardware Wallet Alternative: AirGap enables users to turn any spare smartphone into a cold wallet, removing reliance on proprietary hardware like Trezor.
- No Geographic Restrictions: Unlike Trezor, which is not available everywhere, AirGap is accessible globally to anyone with a smartphone.
- Cost-Effective Security: Users don’t need to invest in expensive dedicated hardware. Any old phone can be repurposed as an offline, air-gapped wallet.

2. Fully Air-Gapped Security Model

- No USB, Bluetooth, or NFC Connectivity: AirGap Vault (the signing app) never connects to the internet, reducing the risk of remote attacks.
- QR Code-Based Transaction Signing: Transactions are created on AirGap Wallet (online device) and signed on AirGap Vault (offline device) using QR codes—eliminating online attack surfaces.
- Mitigation of Supply Chain Attacks: Since users use their own smartphones, there’s no risk of pre-installed malware or tampered hardware during shipping.

3. Advanced Security Features for Zcash Users

- User-Collected Entropy: AirGap allows users to generate their private keys using dice rolls and coin flips, adding an extra layer of randomness beyond traditional RNG chips. This ensures greater unpredictability and protects against potential vulnerabilities in hardware-generated randomness.
Multi-Layered Encryption: AirGap employs advanced cryptographic techniques to secure private keys, ensuring they remain protected even in case of device compromise.

4. Open-Source, Transparent Security

- Community Auditable Code: AirGap is fully open-source, allowing independent audits and ensuring there are no hidden backdoors.
- Trustless Verification: Users can verify the security of the application code themselves, unlike proprietary hardware wallets where firmware updates may introduce unknown vulnerabilities.

Software Deliverables

AirGap Coin Library (Open-Source SDK - TypeScript)

  • Enables Zcash integration for any developer via an open-source library.
  • Handles address derivation, transaction encoding, and signing.
  • Available on GitHub under MIT License for community contributions.
  • Support for Shielded and Transparent transaction signing

ZCash support in AirGap Vault (Mobile App - Offline, Cold Storage)

  • Securely stores Zcash private keys on an offline device.
  • Signs Zcash transactions via QR code-based air-gapped communication.
  • Supports manual entropy generation (dice rolls, coin flips) for enhanced security.
  • Updates Available on iOS, Android and GitHub.

AirGap Wallet (Mobile App - Online, Transaction Creation & Management)

  • Allows users to create and broadcast Zcash transactions. Support for both Shielded and Transparent transaction signing.
  • Provides transaction history, address management.
  • Updates Available on iOS, Android and GitHub.

Detailed proposal - GitHub

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Hi @ashish - Welcome to the forum, and thank you for submitting your grant proposal! We will review it in the upcoming weeks and reach out if we have any questions.

In the meantime, if you have any questions for us, you can post them to this thread or DM us at @ZcashGrants.

Zcash Community - We want to hear your feedback on this grant! You can post your comments to this thread or DM us at @ZcashGrants if you’d like to provide feedback in private.

Thanks!

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Great proposal :+1:

I have 2 questions regarding this proposal. Will the project use PCZT and makes it compatible with other PCZT wallet like Zashi? While I welcome another new wallet for Zcash in the form of AirGap Wallet, it takes more resources to maintain a Zcash wallet than a Bitcoin wallet. So, if for any reason AirGap Wallet in the future doesn’t support Zcash anymore, at least folks can continue to use AirGap Vault with other Zcash wallets.

The 2nd q, was related. What’s your plan if someday Zcash is not supported anymore on AirGap Wallet?

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Hello! Thank you for applying for a grant!

I just watched the introductory video, I assume that’s what most people will do :sweat_smile: I’ll ask some naïve questions to get the conversation started.

The model says that the signing device is completely offline. How does airgap manages updates? How would iOS users update their airgap app without connecting to the app store if they don’t have a rooted devices?

How does Airgap differ from cold storage options offered by Ywallet already?

Airgap claims to be completely free. How does it economically sustain over time?

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I’ll try to answer all questions here.
1) How does airgap manages updates? How would iOS users update their airgap app without connecting to the app store if they don’t have a rooted devices?

There are 2 ways with which AirGap Vault can be updated - online approach and offline approach.
The online approach is pretty simple - you just download it from the web
The offline one only works for Android devices. Android users can update Vault via USB stick or SD card. They just download the package on the external storage and install it from there. Guide.
iOS users can only update their app from Appstore

2) How does AirGap differ from cold storage options offered by Ywallet already?
There are multiple differences between AirGap and Ywallet. A few reasons why AirGap is a better cold storage solution -

  • True Randomness for Seed Generation – Unlike Ywallet that rely on a device’s RNG (which can be manipulated), AirGap supports dice roll and coin flip entropy to generate seed phrases, ensuring verifiable, human-generated randomness for maximum security.
  • Advanced Security features - AirGap includes BIP-39 passphrase protection, BIP-85 deterministic seed derivation, and social recovery, allowing users to add extra layers of security and flexibility to their wallets. These security features are absent in Ywallet.
  • Better UX - AirGap has a much better interface than Ywallet. Ywallet has its own features, but it’s not beginner-friendly. AirGap on the other hand offers a better UX for beginners as well as users who prefer hardcore security. AirGap supports multiple languages, including Chinese, French, Russian, Portuguese, Spanish, and German, making it accessible to a diverse global audience.

3) Airgap claims to be completely free. How does it economically sustain over time?
AirGap is an open-source, self sustainable project developed by Papers * a Swiss company that specializes in building secure, open-source infrastructure for blockchain projects. AirGap’s source code is fully reproducible, meaning the code you see is exactly what gets built into the app.

AirGap is funded through a combination of revenue from its online shop, donations from its community, and grants provided by blockchain ecosystems for integration and support.

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Thank you for your detailed response

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1) Will the project use PCZT and makes it compatible with other PCZT wallet like Zashi?
Your reasoning makes sense. We are not yet that proficient in the Zcash world to know exactly how to handle Partially Constructed Zcash Transactions. Also, we currently do not have support on the Bitcoin side to load and sign PSBTs (Partially Signed BItcoin Transactions), which to my understanding shares some similarities and would follow a similar process. Therefor I don’t think we can offer PCZT signing from the start as this integration effort could be quite significant.

What what look into, is compatibility of the AirGap Vault with Zashi, if we get some support from the Zashi developers. We know the Keystone project very well, which also managed to do a Zashi integration and we think it shouldn’t be too tough, to support that. We also support various third party wallets on Bitcoin (Sparrow, Specter, Nunchuk, Bluewallet) or MetaMask, imToken, Rabby and Blockwallet for EVM chains.

2) What’s your plan if someday Zcash is not supported anymore on AirGap Wallet?
Airgap is completely open source. So if that day comes and the the Zcash community sees value in it, it could do maintenance for the necessary parts. Also, we always use standard key derivation schemes, eg BIP-39, so you could also recover your wallet on a different wallet application.

You can find more information here in our documentation and FAQs: https://support.airgap.it/

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@ashish thank you for your submission. After consideration from @ZcashGrants and sufficient time for the community to provide feedback on the forum, the committee has decided to reject this proposal.

The committee appreciates your grant submission efforts and encourages you to continue as an active member of the Zcash community going forward!

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Thank you for taking the time to review our grant proposal and for allowing the community to provide input during the evaluation period.

While we understand and respect the committee’s decision to reject the proposal, we would sincerely appreciate any specific feedback you could share to help us understand the areas where the submission may have fallen short.

Best.
Ashish (Team AirGap)