SAN FRANCISCO (Reuters) - A senior Apple Inc security expert left for a much lower-paying job at the American Civil Liberties Union this week, the latest sign of increasing activity on policy issues by Silicon Valley privacy specialists and other engineers.

Jon Callas, who led a team of hackers breaking into pre-release Apple products to test their security, started Monday in a two-year role as technology fellow at the ACLU. Prior to his latest stint at Apple, Callas designed an encryption system to protect data on Macs and co-founded communications companies Silent Circle, Blackphone and PGP Corp.

“Jon has unparalleled knowledge about the hazards of surveillance back doors and is also an extremely effective communicator to the public, which is equally important,” said Ben Wizner, director of the ACLU’s Speech, Privacy and Technology Project.

Wizner said he expects Callas to help the group resist governments demanding access to company platforms for surveillance of users and to weigh in on issues including fairness and transparency in artificial intelligence.

Past tech fellows at ACLU joined earlier in their careers, but the ACLU wants seasoned experts. “It’s critical for organizations like the ACLU to address the asymmetry of expertise between entities like the National Security Agency and Silicon Valley corporations and those of us who are trying to rein them in,” Wizner said.

Callas’ move comes after a year of unprecedented activism by rank and file engineers at Alphabet Inc’s Google, Facebook Inc and other technology powerhouses under fire for enabling the spread of misinformation and government-led misdeeds.

Callas said he felt particular kinship with Google employees pressing to have more of a say in the company’s prospective deal to return to mainland China with a censored search engine.

“A bunch of people have in fact woken up and said `Where are we, where are we going?’” Callas said. “These employees are wanting more discussion and access to what’s going on.”

Callas said phone makers had improved security and he wanted to see progress continue and widen without companies succumbing to pressure to install back doors.

Famed cryptography author Bruce Schneier encouraged Callas to take the ACLU post. Schneier said he was seeing a broader sense of public obligation, with a hundred applicants for a recent opening at the nonprofit Electronic Frontier Foundation.

But he said there need to be more ways to contribute to the public welfare and that technology still lags fields like law, where charity work is expected.

“At Harvard Law School, 20 percent of graduates go into public services and they have a meeting about it because they are upset it is so low,” Schneier said. “Computer science is at zero. Can we get it to 10 percent?”

At the biggest annual security conference, March’s RSA, Schneier is coordinating a daylong series of talks on “public interest technology” with funding from the charitable Ford Foundation.

“Discrimination in the 21st century is algorithmic. Free-speech abuses in the 21st century are about platforms,” Schneier said. “It is no longer the case that these worlds are separate.”