Signal, the private messaging app that had a 4,200% increase in downloads in January, is launching a payments feature using mobilecoin (MOB). Signal founder Moxie Marlinspike has been an adviser to the project since 2018.

The goal of MOB, which is based on Stellar blockchain technology, is to be able to work efficiently on mobile devices while also protecting users' privacy. The launch on Signal has long been rumored, dating back to when Facebook announced plans to launch its libra stablecoin in early 2019.

MOB stands out from a pack of messenger-native crypto coins because it has actually launched. Telegram’s TON was nuked by U.S. regulators; Facebook’s libra (now diem) remains in a state of near-completion.

At this time, the MOB payment feature will only be available to users in the U.K., and only on iOS and Android. Desktop support is not included. 

"I'm terrified for Signal," Matthew Green, a cryptographer at Johns Hopkins University who sits on the Zcash Foundation board, told Wired, adding: 

On the other hand, integrating privacy-oriented cryptocurrencies into relatively popular communications apps may give users an attractive onramp and interface to enter into the world of crypto.

In a blog post announcing the launch of the feature in beta, the company said users can link a MOB wallet to Signal, send funds, receive funds, keep track of their balances and review transaction histories.

“As always, our goal is to keep your data in your hands rather than ours; mobile coin’s design means Signal does not have access to your balance, full transaction history, or funds,” Signal wrote. “You can also transfer your funds at any time if you want to switch to another app or service.”

Mobilecoin is currently only trading on FTX.