How something like a credit default swap net to zero? If I sell you one, I create a new instrument which has a stream of income (so it can be valued theoretical

How something like a credit default swap net to zero? If I sell you one, I create a new instrument which has a stream of income (so it can be valued theoretically). But if the securitIes that are insured against are to opaque to be valued, there is now unknown potential liability. As it happened with AIG, they had a situation where those liabilities became real, and to large to honor. It was as if they created this huge debt from thin air, with not enough collateral. I guess in a sense since their loss was supposed to be Goldman Sachs gain, there is a netting to zero, but that seems semantic. In would think of netting to zero as meaning something like a zero sum gameve where no participant can win or lose more money that existed.