"The United States government has demanded that Apple take an unprecedented step which threatens the security of our customers," said Apple (AAPL 0.64%) CEO Tim Cook in an open letter published on Tuesday. "We oppose this order, which has implications far beyond the legal case at hand."

Apple CEO Tim Cook. Image source: Apple.

In the controversial letter, Cook explains why Apple is not going to build a back door to the iPhone for the FBI to access customer information.

Republican candidate Donald Trump disagrees with Apple's refusal.

"Who do they think they are?" Trump said on Wednesday in an interview with Fox & Friends, according to Politico. "They have to open it up."

Who is right?
First, it's worth noting that Apple isn't refusing to give the FBI any information the company has. The FBI's request to Apple goes much deeper than a search warrant for information already in Apple's possession.

"Up to this point, we have done everything that is both within our power and within the law to help them," Cook explained.

But now the U.S. 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.

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.

iPhone 6s. Image source: Apple.

Cook noted that while Apple believes the FBI's "intentions are good," the company believes creating what would be intended to be used only as a temporary backdoor could put every customer's data at risk.

The FBI may use different words to describe this tool, but make no mistake: Building a version of iOS that bypasses security in this way would undeniably create a backdoor. And while the government may argue that its use would be limited to this case, there is no way to guarantee such control.

Later in the letter, Cook provides a useful analogy to explain the danger of creating a back door:

In the physical world, it would be the equivalent of a master key, capable of opening hundreds of millions of locks -- from restaurants and banks to stores and homes. No reasonable person would find that acceptable.

But Trump strongly disagrees with Cook.

"I agree 100% with the courts," Trump said. "In that case, we should open it up." Trump was referring to the specific case this FBI investigation was about: the San Bernardino attack that killed 14 people. Trump also believes the approach to customer security for digital security overall should be one that is "open."

"I think security, overall, we have to open it up and we have to use our heads. We have to use common sense," Trump continued.

One key concern in this argument for Apple investors and customers is whether Apple could be forced to go back on its word on not having a back door. But if Apple's findings are true, that there is "no precedent" of an American company being forced to expose customer data to a greater risk of an attack, then it's probably unlikely the company will be forced to change its policy.

Who do you think is right, Cook or Trump?