Jon Callas co-founded the widely-used email encryption software PGP and the secure-messaging system Silent Circle that sells the Blackphone. Apple’s decision to rehire Callas comes after rumors that the company is working on improving the security of its iOS devices in such a way that even Apple can’t hack. Earlier this year, Apple was engaged in a legal battle with the US Department of Justice over a court order asking the company to help the FBI unlock iPhone 5C of San Bernardino shooter Syed Farook.
Source: https://thehackernews.com/2016/05/apple-security-expert.html