Chatting on Kakao Talk will become more secure with a new hidden chat feature that has end-to-end encryption for all messages.
Secret Chat is a chat room that requires messages to be read with a decryption key stored in a user's mobile device, Daum Kakao, the South Korea-based operator of the service, said in a release.
That means the messages cannot be intercepted by outsiders, even if they're going through servers, it said.
Users can initiate Secret Chat with others and keep them open even when the app itself is closed. One to one chats are supported in the secret mode, with secret group chats to follow in the first quarter of 2015.
The move comes after media reports in October saying that users were abandoning the app after South Korean President Park Geun-hye vowed to prosecute people spreading rumors about her on Kakao Talk.
In an apparent move to allay fears, the company reduced the amount of time chat histories are stored on its servers to two or three days from three to seven days.
"The recent rise in interest in privacy concerns in turn increased requests from our users for the option to chat in even stronger privacy," a company spokeswoman said in an email when asked about the reasons for the new Secret Chat function.
"We have also received continuous requests from our users to add a feature that allows them to decline invites from group chatrooms. While many of our users find group chats extremely useful, there are some users that prefer to keep their chats more private, and stick to conversations with strictly selected few."
Daum Kakao said Monday that it responds to legal warrants for access to information that are issued by South Korean courts or prosecutors, she said, adding the company does not comply with censoring requests by China.
The Secret Chat feature, as well as a decline group chat invites feature, is available with the latest version of the app, 4.7.0, for Android devices, with the corresponding iOS version to follow.
Kakao Talk now claims 164 million users around the world, with about 93 percent of smartphone users in Korea using the app.