“In order to ensure the government is added to the conversation in secret, GCHQ’s proposal would require messaging apps, service providers, and operating systems to change their software so that it would 1) change the encryption schemes used, and/or 2) mislead users by suppressing the notifications that routinely appear when a new communicant joins a chat.”

Source : Apple and WhatsApp condemn GCHQ plans to eavesdrop on encrypted chats | UK news | The Guardian