REUTERS/Stephen Lam

Sen. Al Franken (D-Minn.) on Wednesday called on Apple to more fully explain how the facial-recognition system on its new iPhone X will protect the privacy of its users and whether the data will be shared with law enforcement.

The request, in a letter sent to Apple chief executive Tim Cook, echoes concerns that privacy advocates raised following the announcement of the new system on Tuesday. The technology uses several sensors to map the faces of users and stores the resulting data on the device itself, allowing users to later unlock the device or use the Apple Pay app my merely glancing at it.

“Since the announcement,” Franken wrote, “reporters, advocates, and iPhone users have raised concerns about how Face ID could impact Americans’ fundamental right to privacy, speculated on the ways in which Apple could use faceprint data in the future, and questioned the quality and security of the technology.”

He called on Apple to detail how the device protects the facial data from possible hackers and asked whether the data will be used for any purpose other than for the facial-recognition system. Franken, who has scrutinized the rising use of facial-recognition technology for several years, also questioned whether Apple has any intention to ever store the facial data in a central database, how it would notify users of a future breach to that database and how Apple plans to respond to law enforcement requests for facial data.

Apple declined to comment Wednesday evening. In announcing the technology on Tuesday, company officials portrayed the facial-recognition system as safe, efficient and reliable. The company said the facial data would not be transmitted over the internet where it could be vulnerable to interception. The technology was among the most highly touted features of the iPhone X, a $999 high-end device designed to celebrate the 10th anniversary of the original iPhone in 2007, though analysts expect facial recognition will eventually be released on other models. Some Android smartphones also use the technology.

While privacy advocates raised concerns about the technology and the possibility that it could lead to a wider spread of facial recognition, some also praised Apple for using the technology in a way that users control themselves. Some also said that the facial-recognition system could enhance the security of users by making it harder for impostors to unlock devices.