Mathematician turned financier's net worth up 15% in past 12 months. His Medallion fund surged 80% last year despite market collapse; up 12% so far this year. MIT grad cracked codes for U.S. Department of Defense during Vietnam War. Founded quantitative hedge fund Renaissance Technologies 1982. Firm hires Ph.D.s instead of M.B.A.s; uses algorithms to exploit subtle mispricings in stock, bond, commodities markets. Launched RIEF fund geared toward institutional investors 2005. Also runs futures-oriented fund RIFF. Firm's total assets: $17 billion.