Four coalitions representing Apple, Microsoft, Google, Amazon, and other major tech companies have published an open letter expressing their concerns over a controversial US bill that would require smartphone makers to decrypt data on demand. The letter, published this week, is addressed to the bill's sponsors, Senators Richard Burr (R-NC) and Dianne Feinstein (D-CA), and signed by four industry groups: Reform Government Surveillance, the Computer and Communications Industry Association, the Internet Infrastructure Coalition, and the Entertainment Software Association. In addition to Apple, Microsoft, Google, and Amazon, the coalitions represent companies like Facebook, Netflix, eBay, and Dropbox.

"Any mandatory decryption requirement, such as that included in the discussion draft of the bill that you authored, will to lead to unintended consequences," the letter reads. "The effect of such a requirement will force companies to prioritize government access over other considerations, including digital security." The groups go on to note that adhering to the bill's requirements would make any products or services vulnerable to exploitation by "bad actors," and that it could have major ripple effects. "[N]o accessibility requirement can be limited to U.S. law enforcement," the letter continues, "once it is required by the U.S., other governments will surely follow."

An official draft of the bill was published last week, in the wake of Apple's standoff with the FBI over access to an iPhone used by one of the shooters in the San Bernardino terrorist attack. The bill has been met with strong resistance from civil liberties groups like the ACLU and Electronic Frontier Foundation, as well as Senator Ron Wyden (D-OR), who has said he will filibuster it.

But the bill's backers have sought to dispel concerns over privacy and security, arguing that it is critical to law enforcement. "No entity or individual is above the law," Feinstein said in a statement last week. "The bill we have drafted would simply provide that, if a court of law issues an order to render technical assistance or provide decrypted data, the company or individual would be required to do so."