WASHINGTON -- President Barack Obama on Thursday sent his strongest signal yet that he wants the government to get tougher with Wall Street, appointing a former prosecutor to head the Securities and Exchange Commission for the first time in the agency's 79 years.Mary Jo White, a former U.S. attorney in Manhattan, has an extensive record of prosecuting white-collar crime. She won convictions in the 1993 World Trade Center bombing and the 1998 terrorist attacks on two U.S. embassies in Africa, and put crime boss John Gotti away.If confirmed, she will have the job of enforcing complicated regulations written in response to the worst financial crisis since the Depression.Obama also re-nominated Richard Cordray as head of the Consumer Financial Protection Bureau, created after the financial meltdown. The president used a recess appointment last year to circumvent Congress and install Cordray. That appointment expires Dec. 31.White, now in private practice, would take over at the SEC from Elisse Walter, interim chairwoman since Mary Schapiro resigned in December. White was the first woman to be named U.S. attorney in Manhattan, one of the top jobs in law enforcement.Colleagues and politicians describe her as tough and fiercely competitive. She brings a wealth of legal bona fides to an agency that, critics say, failed to act aggressively to charge top individuals at the nation's largest banks who may have contributed to the financial crisis.Under Schapiro, the SEC brought civil charges with record penalties against Goldman Sachs, JPMorgan Chase and Citigroup, among others. But top executives went unscathed.James Cox, a Duke University law professor, predicted White will push the SEC away from "being just a tollkeeper" collecting settlements and make it a forceful agency that brings meaningful sanctions against senior individuals.