According to program researcher Jane Manchun Wong, Twitter is working on end-to-end encryption of direct messages sent over the social network.

“I’m seeing signs that this feature is being worked on on Twitter for Android,” Wong wrote in a tweet. chirp, accompanied by lines of code that highlight links to encryption keys. Twitter CEO Elon Musk later responded to Wong’s tweet with a winking emoji;

DMs with end-to-end encryption put Twitter’s messaging platform on par with apps like Signal and WhatsApp, ensuring that conversations between users are seen only by the sender, not by third-party snoopers.

Twitter started working on encryption for DMs under the name “secret conversations” in 2018, but that feature never materialized. Musk has previously defended the privacy-focused encrypted messaging platform Signal, arguing that it makes secure communication a priority for the service.

In related developments, Musk said that Twitter’s $8-per-month subscription plan will be restarted later than originally planned. Musk announced in a tweet Tuesday night that Twitter Blue Verified will be back on November 29 “to make sure it’s trustworthy.”