The basic idea is this: if you had say an ICO or DAO that allowed you to mint tokens by using ETH, with a contract like this you could also allow someone to send bitcoin to a specific address, prove the transaction occurred and mint some tokens once proof has been supplied. Since the public key is revealed, you can derive an ethereum address from the bitcoin sender and mint tokens directly back to their original key.
Take a look at the contract here: https://github.com/James-Sangalli/BitDEX/blob/buy-tokens-on-eth-with-btc/contracts/BuyTokensWithBTC.sol
IMPORTANT NOTE: this is just a fun experiment, don’t use it in production, at least not yet 🙂
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