Vitalik suggests private NFTs using ‘stealth addresses’ to hide the owner’s identity

Ethereum Founder Vitalik Buterin suggests the idea of private NFTs whereby the owner would not be known through blockchain data.

The concept was added to an Ethereum Research post focused on adding an “ERC721 Extension for zk-SNARKs.”

Idea: stealth addresses for ERC721s.

A low-tech approach to add a significant amount of privacy to the NFT ecosystem.

So you would be able to eg. send an NFT to vitalik.eth without anyone except me (the new owner) being able to see who the new owner is.https://t.co/UdqK6NAYjn

— vitalik.eth (@VitalikButerin) August 8, 2022

ERC721 extension for zk-SNARKs

The extension to ERC721 (the NFT standard) was proposed by Nerolation, who stated that he believed his methodology was “the exact implementation of what Vitalik described” when talking about private POAPs.

Vitalik spoke about the potential need for private Soulbound tokens (SBTs) in his article introducing the SBT concept to the world. He stated,

“Privacy is an important part of making this kind of ecosystem work well… If, one day in the future, being vaccinated becomes a POAP, one of the worst things we could do would be to create a system where the POAP is automatically advertised… to let their medical decision be influenced by what would look cool in their particular social circle.”

The suggestion of using ZK-SNARK compatible ERC721 tokens attempts to solve this by using stealth addresses that include a hash of the user’s address, the token ID, and a secret of the user.

The information is then added to a Merkle tree on-chain, with the tokens being stored at “an address that is derived from the user’s leaf in the Merkle tree.”

To prove ownership of the token (NFT), an address would have to give the stealth address “access to a private key” so that when a message is signed, the collated information can be passed to a leaf of the Merkle tree. The circuit would then be able to compare the “calculated and user-provided roots for verification.”

Regular stealth…