In a discussion on encryption and data security, Comey said that Apple and Google’s decision in 2014 to encrypt their mobile devices to improve user privacy angered the former FBI Director. He wrote in the book that the decision “drove me crazy.” He added that Silicon Valley didn’t engage in “true listening” with the FBI and said executives “don’t see the darkness the FBI sees.”

“I found it appalling that the tech types couldn’t see this,” he wrote. “I would frequently joke with the FBI ‘Going Dark’ team assigned to seek solutions, ‘Of course the Silicon Valley types don’t see the darkness–they live where it’s sunny all the time and everybody is rich and smart.’”

Major tech companies, including Apple and Google, have been at odds with some in the law enforcement community for years over encryption. And Apple CEO Tim Cook has been one of the more outspoken proponents of encryption and user privacy. Cook has said in no uncertain terms that privacy is critical and Apple would not comply with any attempts by the U.S. government or any foreign government to build so-called “backdoors” into his company’s products that would make it easy for law enforcement to access user data.

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“While we believe the FBI’s intentions are good, it would be wrong for the government to force us to build a backdoor into our products,” Cook wrote in an open letter on the topic in 2016. “And ultimately, we fear that this demand would undermine the very freedoms and liberty our government is meant to protect.”

Those in law enforcement, however, have decried the move by tech’s biggest companies. They argue that encrypting data and not giving law enforcement a backdoor to access it puts innocent people in harm’s way and stands in the way of important law enforcement work.

The standoff has created a profitable opportunity for security firms that work exclusively on finding ways to break into iPhones and Android devices. And it’s believed that one solution, called GrayKey, is being put into action across the U.S. by law enforcement agencies who want to break into devices. The company behind GrayKey, GrayShift, has developed a solution for bypassing security features in iPhones, according to Vice. And now police stations and the FBI have reportedly invested in the technology to access data.

Still, the simplest solution in law enforcement’s opinion is for Apple and Google to provide easier access to their devices. But at least for now—despite concerns from Comey and others—that doesn’t appear likely.

Neither Apple nor Google immediately responded to a Fortune request for comment on Comey’s book.