SegWit introduces a fundamental change to bitcoin: the “AnyOneCanSpend address”, or essentially a blank signature for transactions. SegWit uses an “AnyOneCanSpend” address so that transactions will be validated and recorded into blocks, even though the sender/receiver signature data is separated. Normally, an “AnyOneCanSpend” output (as its name implies) would allow any miner to spend the funds associated with that transaction; therefore, SegWit would introduce new rules for interpreting “AnyOneCanSpend”. This means that miners could not take advantage of that output address to inappropriately spend the funds associated with all SegWit transactions.