I have discovered NFTs and ETH recently and would like to build a marketplace like opensea but allows resale of NFTs that are already minted on various block chains(ETH, FLOW). Starting with just ETH, when some one comes to marketplace to sell their NFT, I would like to :
- Verify the ownership of NFT that the seller is claiming to resell on my marketplace. How do I do this? Can I take the seller’s wallet’s public information and query the blockchain somehow?
- when the seller sends the NFT to the buyer and claims that he sent it, how do i verify that the nft was safely sent to the buyer’s wallet?
From what I have read so far, etherscan seems to have a way to keep track of transactions and also extract NFT metadata to verify ownership of the NFT, how can I do the same?