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Zero Pass

Users can verify their phone number or solve captcha in this app to mint a NFT. Other apps can read the NFT to validate phone number, captcha etc. zk is used for anon profile.

Zero Pass

Created At

ETHIndia 2022

Winner of

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🏊 StackOS — Pool Prize

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🥈 Marlin — Best Use

Project Description

Validate Phone Number with NFT.

Imagine a user needing to verify phone number in 100 websites. He will have to send his phone number to these 100 websites which is bad for privacy and he will enter OTP 100 times costing time and money.

Instead, in "Zero Pass", the user can verify the phone number once and a NFT can be minted to the user. Other platforms, which integrate "Zero Pass", can validate the NFT to validate the phone no.

Once a phone no is verified in "Zero Pass", users can mint a NFT in 3 ways.

  • Store phone number directly in NFT metadata.
  • Store hash of phone number in NFT metadata for pseudonymous profiles.
  • Zk proof for anonymous profiles.

Validate Captcha with NFT

Solve captcha in "Zero Pass" and mint a NFT. Other platforms can validate the NFT to see if the user has solved captcha.

This results in better UX and reduces the need for apps to block Tor IP's to reduce spam.

The NFT's can be soulbound or users can buy captcha NFT's if they want to avoid solving captcha's.

Using "Zero Pass" to issue airdrops

Various web3 entities want to issue airdrops to as much users as possible. One popular way to do this is to create a Google form, ask for Twitter profile and wallet address.

The problem with that is, spam users game this by using bots and API's. Spam users create multiple Twitter profiles and follow themselves. Also, they create multiple crypto wallets with dummy transactions.

Validating the phone number can reduce spam accounts but many web3 users are concerned with privacy.

So, they can use "Zero Pass" to validate the users phone number though NFT.

Potential partners.

Biconomy and Lens protocol support gasless transactions. But it can be prone to either spam attacks or reliance on web2 like Google sign in. They can use "Zero Pass"

World Coin, Huddle01, Brave browser and Deso(Bitclout) can use "Zero Pass" instead of web2 kyc.

How it's Made

When we solve captcha in web2 world, we are training Google ML to be better in self driving cars. So, we planned to map captcha images and text in the NFT metadata so that other dev's can use it to train their ML. Since these things take time to plan and code, we have planned to work on this after the Eth India hackathon 2022.


Cartesi Blockchain OS may be useful for this but requires deeper understanding of Cartesi from our team. Carlo from Cartesi helped us understand what is possible and what is not with Cartesi. We plan to explore what problems Cartesi can solve after the Eth India 2022 hackathon.


We, as a team, tried to understand, what zk is before the hackathon and it was an inspiration for our team name too. The maths of it was complicated though. Getting explanation of zk tech from physical people in Mina protocol, Marlin, Polygon and zkBob, did signicantly help us.

Marlin showed us that zk can be outsourced to Marlin.

Mina protocol showed that zkapps can be used for "Zero Pass" without needing us to understand or implement zk from scratch.

Polygon also explained about zk and Polygon ID. We learnt about Circom and iden3. "Zero Pass" could partner and compete with Polygon ID as there are some similarities.

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