On Koum's post announcing his departure, Zuckerberg commented, "I'm grateful for everything you've done to help connect the world, and for everything you've taught me, including about encryption and its ability to take power from centralized systems and put it back in people's hands".
The head of popular messaging service WhatsApp is planning to leave the company because of a reported disagreement over how parent company Facebook is using customers' personal data.
Another person familiar with the matter said Mr. Koum won't leave immediately and is expected to walk away with his Facebook stock nearly fully vested. Koum resisted his parent company's attempts to pull more data from WhatsApp users for advertising purposes.
Facebook has taken steps in recent months to generate revenue from WhatsApp, which unlike Facebook's flagship social network does not have advertising.
In 2015, Malcolm Turnbull confirmed he used secure apps including WhatsApp for messaging, saying: "Probably the least secure form of messaging is SMS or text messaging". The company once said it was built "around the goal of knowing as little about you as possible".
Despite the Post's reporting, Koum portrayed his departure in positive terms. Acton isn't involved with WhatsApp anymore, having left it in November to later join Signal Foundation.
-Kirsten Grind contributed to this article.