NFT Bridges

Back to basics

An NFT (or Non-Fungible Token) is a non-interchangeable digital asset backed by a blockchain system. While a unit of Bitcoin or Ether is interchangeable, any two units of the token will have the same exact value, this is not the case for NFTs. NFTs are “one of a kind” tokens, and they are uniquely identifiable. This is why they are usually used to represent collectibles (like art, music, games, or even real estate) or unique digital resources (like domain names or identities). They are the ultimate way to represent ownership and scarcity of digital resources. How can one own an image on the Internet when anyone can copy-paste it and replicate it? Well, NFTs try to tackle this problem; they won’t be able to prevent others from copy-pasting it, but at least there’s a way to track back its ownership directly to you.

The asset fragmentation problem

So what has changed in the NFT space since the CryptoKitties fever of 2017? Mainly, NFT standards have improved; L2 solutions (like Metis or Arbitrum) are now a reality; and new blockchain networks with smart contract support beyond Ethereum (like Solana or Polygon) are in mainnet. In 2017 we could only mint our NFTs in Ethereum; now, we can have our NFTs scattered all around the blockchain space, from Solana, to Metis, to Ethereum.

NFT Bridges

So how can we remove these NFT silos between different L2 solutions and Layer 1? We need a protocol that supports the creation and transfer of NFT across multiple layers, i.e. an NFT bridge. Is there already any implementation of an NFT bridge? Not that I am aware of, but different designs are being discussed (such as the aforementioned ones). For illustration purposes, let me walk you through the approach that Pavel Sinelnikov proposed in his post (which, from what I infer from the title of the images shared, could end up being the approach that gets implemented by Metis).

And its use cases

But what kind of use cases do NFT bridges unlock? Why would we want to migrate NFTs from one layer to another? In the near future, we can expect limited resources from the Internet to be represented with NFTs, like for instance domain names or identities. A user looking to own the domain name example.dapp to deploy his new decentralize service can mint a new NFT in a Layer 1 smart contract that provides a registry of available domains. This user can afford the cost and the wait of minting this in L1, but from there on, he doesn’t want to pay the gas cost of every single change to its domain name NFT metadata. Consequently, after minting it, he chooses to migrate his domain name NFT to an L2 solution.

Towards an interoperable ecosystem

One of the big promises of blockchain systems is the removal of all of those data silos that we currently have on the Internet. When one talks about the Cloud, it may seem as if it was a single entity holding all our data on the Internet. But this is far from the truth. The Internet is full of data silos kept hostage by companies. We need to prevent this from happening to our assets in the blockchain space. NFT bridges and other interoperability efforts are already paving the way towards the “blockchain without silos” that we all want and need.



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