I have trouble understanding the underlying mechanism for the UJO Music Portal, that helped Imogen Heap sell her album online. There is a smart contract that enables people to pay using ETH with MetaMask and in the end they receive a link to download the song.
Is the link to the song stored in the smart contract? If so, can someone access the smart contract to read the link without paying?
I'm basically trying to come up with a mechanism to pair documents and payments in a smart contract. If you don't pay you should not be able to access the document/the link to the document/the decryption key to the document.
Thanks for your inputs.