All miners 'compute on' the same blockchain. That is, they compete for the priviledge of adding the next block for the mining and transaction rewards that come

All miners 'compute on' the same blockchain. That is, they compete for the priviledge of adding the next block for the mining and transaction rewards that come with it. Thus, NASDAQ transactions (as all bitcoin transactions) are secured by the hashing power of the global network. In short, that's why NASDAQ is using bitcoin rather than their own blockchain app, as it is the most secure blockchain in terms of a computational attack.