Many financial firms may not be prepared for the interest-rate increases that will be needed as the U.S. economic recovery gains traction, the number-two official at the Federal Reserve said Friday. Kohn Fed Vice Chairman Donald Kohn said in a speech at the Federal Deposit Insurance Corp. that “many banks, thrifts, and credit unions may be exposed to an eventual increase in short-term interest rates.” “In light of the uncertain course of interest rates, financial intermediaries face significant challenges in managing their interest rate exposures,” the top Fed official said.