By Jon Herskovitz AUSTIN, Texas (Reuters) – Former security contractor Edward Snowden, facing arrest if he steps foot on U.S. soil, said the changes the American government and private companies have made about managing massive amounts of data helped vindicate his leaks of classified material. Speaking to a sympathetic and tech-savvy crowd at the South by Southwest conference in Austin, Texas, via a video link from Russia, Snowden added that the U.S. government still has no idea what material he has provided to journalists. Last year, Snowden, who had been working at a National Security Agency facility as an employee of Booz Allen Hamilton, leaked a raft of secret documents that revealed a vast U.S. government system for monitoring phone and Internet data.