Messaging tool appears to have been blocked on mainland, but experts say users don\u2019 t have to worry about encryption being compromised<\/b>
\nMainland WhatsApp users reported partially restored functions on Wednesday after experiencing trouble using the instant messaging tool on Tuesday.
Some users now appear to be able to send sound clips and photos, after reports of service disruptions a day earlier.
Security experts said despite the service disruption, so far it does not appear communications security had been compromised.
China\u2019s WhatsApp users find \u2018blocked\u2019 messaging functions partially restored
Tests with South China Morning Post reporters stationed in Beijing, Shanghai and Guangzhou showed different results, with Shanghai users experiencing the most difficulties.
A spokeswoman with Facebook, which owns WhatsApp, declined to comment on the service disruption on the mainland.
The Post \u2019s staff members in Guangzhou on Wednesday had no issues sharing text messages, videos, pictures or sound clips with local or overseas WhatsApp users.
But in Beijing, while reporters could receive most multimedia content, photos were a problem. Some pictures sent from overseas users could be displayed only as pixelated previews and couldn\u2019 t be downloaded in full.
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Two users in Shanghai failed to send or receive pictures using local mobile networks. One also failed to register on WhatsApp with a local number.
Foreign ministry spokesman Lu Kang said he had no information on the issue when asked by reporters on Tuesday, Associated Press reported.
Gerardo Salandra, co-founder of the Artificial Intelligence Society of Hong Kong, said secured communications on WhatsApp had yet to be compromised despite the service interruptions.
\u201cThe government is blocking WhatsApp on a network level, meaning they can see something was sent, but not what it is, \u201d said Salandra, who added that the best way to avoid interruptions of service on the mainland was to install a virtual private network.
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Professor Keith Martin, a cryptography and cybersecurity expert at Royal Holloway, University of London, agreed that it was possible for the government to block the transmission of images and videos on WhatsApp, but that it still could not read messages.
Martin said that on WhatsApp, text messages were sent directly between users in encrypted form, but images and videos needed to be uploaded to an internet database before being downloaded to the receiver\u2019s phone.
\u201cIt\u2019s definitely possible someone is blocking the internet address where the large files are retrieved from, \u201d Martin said. \u201cIt feels like someone is sending a signal to people \u2013 maybe we can\u2019 t stop WhatsApp completely, but we can interfere with it.\u201d
Additional Reporting by Josh Ye and Viola Zhou<\/p>\n