The director of the FBI has called for a "robust" debate over the use of encryption, but has admitted there may be no easy way to protect both security and privacy.
FBI chief James Comey warned that the increasing use of strong encryption will make it harder for law enforcement to access email or other digital conversations.
"There is simply no doubt that bad people can communicate with impunity in a world of universal strong encryption," he said in a post for the Lawfare blog, and warned this will have an impact on public safety.
He wrote: "That tension is vividly illustrated by the current ISIL threat, which involves ISIL operators in Syria recruiting and tasking dozens of troubled Americans to kill people, a process that increasingly takes part through mobile messaging apps that are end-to-end encrypted, communications that may not be intercepted, despite judicial orders under the Fourth Amendment."
Thanks to the Edward Snowden revelations about pervasive internet snooping by US and UK intelligence agencies, tech companies have been turning to encryption to protect their customers' conversations. This has led to claims from law enforcement that important sources of intelligence are 'going dark'.
"My job is to try to keep people safe. In universal strong encryption, I see something that is with us already and growing every day that will inexorably affect my ability to do that job," Comey said.
Privacy campaigners and tech companies, in contrast, argue that the use of encryption is essential to protecting freedom of speech; the United Nations recently said the same.
Banning encryption is, in any case, all but impossible and likely to be vastly counterproductive. As such, working out how to prevent criminals from plotting in secret while protecting privacy is likely to be a difficult balancing act, something that Comey also acknowledges.
"It may be that, as a people, we decide the benefits here outweigh the costs and that there is no sensible, technically feasible way to optimize privacy and safety in this particular context, or that public safety folks will be able to do their job well enough in the world of universal strong encryption," he said, calling for a "robust debate" to resolve the issue.
"Those are decisions Americans should make, but I think part of my job is make sure the debate is informed by a reasonable understanding of the costs," he said.
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