Can math and bitcoin solve the problem of trusting a third party to run an honest bitcoin-dollar exchange?

This is a Compare & contrast on how math does it for Bitcoin & how the pros do it for stocks vs. "MtGox" type exchange.
http://szabo.best.vwh.net/ttps.html

For Bitcoin/fiat exchange one needs traditional segregation of duties. e.g. 4 peers:  broker/exchange/clearinghouse/custodian. ~ Nick Szabo

Some segregation of duties is far better than none, but more is better & Nakamoto consensus allows much more to be much cheaper. ~ Nick Szabo