Apple has been ordered to unlock an iPhone belonging to Syed Farook, one of the San Bernardino gunmen, by building a backdoor into its iOS software.
However, Apple has said that it will challenge the decision, warning that it sets a dangerous precedent that would undermine the privacy of all iPhone users.
Apple went as far as publishing a letter on its website explaining the circumstances of the case and why it feels that the obligation to unlock the iPhone is wrong.
"The US government has demanded that Apple take an unprecedented step which threatens the security of our customers. We oppose this order, which has implications far beyond the legal case at hand," said the letter, signed by CEO Tim Cook.
"This moment calls for public discussion, and we want our customers and people around the country to understand what is at stake."
The problem for Apple is that the FBI has demanded a backdoor to the iOS platform so that it can access Farook's iPhone. This would be a step too far, according to the letter.
"Up to this point, we have done everything that is within our power and within the law to help them. But now the US government has asked us for something we simply do not have, and something we consider too dangerous to create. They have asked us to build a backdoor to the iPhone," wrote Cook.
"Specifically, the FBI wants us to make a new version of the iPhone operating system, circumventing several important security features, and install it on an iPhone recovered during the investigation.
"In the wrong hands, this software - which does not exist today - would have the potential to unlock any iPhone in someone's physical possession."
Cook underlined that doing this would be a threat to the freedom of US citizens - and others worldwide - and that it will challenge the order for as long as possible.
"We are challenging the FBI's demands with the deepest respect for American democracy and a love of our country. We believe it would be in the best interest of everyone to step back and consider the implications," he said.
"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. And ultimately, we fear that this demand would undermine the very freedoms and liberty our government is meant to protect."
The use of encryption in tech tools is becoming an increasingly thorny political issue. The UK government has also mooted plans to limit its use to allow security agencies to access data on devices, something that tech companies have strongly opposed.
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