Apple CEO Tim Cook explained on Wednesday evening the company’s opposition to creating a “back door” for officials to get around security on its devices, saying it would be equivalent to creating “cancer.”

“The only way we know would be to write a piece of software that we view as sort of the software equivalent of cancer. We think it’s bad news to write, we would never write it, we have never written it, and that is what is at stake,” Cook said in an interview with ABC’s David Muir.