NFT Bridges

Metis
9 min readOct 17, 2021

By Alfonso de la Rocha

Fighting asset fragmentation in blockchains

The word on the street is that NFT fever is not over, and a single search in your search engine of choice will definitely confirm it. News about the release of an interactive NFT Platform, the first-ever NFT trophy for UEFA’s goal of the tournament, or pictures of unique monkeys and giraffes all over social media, from Twitter to Instagram. But what exactly is an NFT, and more importantly, where do these NFTs actually live?

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 first wide-spread standard for the implementation of NFTs was Ethereum’s ERC-721. This ERC provides a standard API for the implementation of NFTs and its basic functionalities. Units of an NFT in the contract’s implementation are represented with a unique ID (this is what makes them non-interchangeable), and the kind of functionalities exposed by the standard are the straightforward ones that anyone would expect: transfer the ownership of a token; approve certain rights over the token for an address; check the balance and ownership of tokens in the contract for an address, etc.

NFTs are nothing new. Those of you who have been here for a while may recall how in 2017 the priciest CryptoKitties were trading at a record high of $1 million USD when EIP-721 was still in a draft state. L2 solutions weren’t a thing back then, and the interest in NFT kitties was such that the great majority of transactions in the Ethereum network involved the CryptoKitties’…

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