A method comprising: providing a first transaction specifying an output amount of a digital asset to greater than pointed to by its inputs, wherein an output of the first transaction comprises a locking script specifying a condition; over a side channel, receiving an input from each of multiple users, and adding each received input to the first transaction; and once a target is reached, whereby the total input amount pointed to by the inputs of the first transaction is equal to or exceeds the output amount, causing the first transaction and a second transaction to be published to a blockchain network to be recorded in a blockchain. The second transaction comprises an input pointing to the output of the first transaction and comprising an unlocking script meeting said condition. The condition requires the unlocking script to include a media key enabling the users to access the item of media content.