The Chinese government has effectively blocked the encrypted version of Wikipedia, cutting off easy access to the free online encyclopedia via its alternative HTTPS address which has been supported since October 2011.

China’s move comes ahead of the anniversary of the sensitive and highly controversial Tiananmen Square protests of 1989, also known as the June Fourth Incident in Chinese.

Users could previously circumvent the Chinese government’s ban of hundreds of articles on the HTTP version of Wikipedia with the HTTPS web address, but according to Chinese web monitoring site GreatFire, the government has put an end to this starting May 31.

The Great Firewall (as China’s censorship mechanism is commonly referred to) started banning access to the encrypted version of Wikipedia through port blocking – by blocking port 443 where HTTPS connections are typically established, users can only visit port 80 where HTTP connections are on.

“The HTTPS version of Wikipedia is blocked while the HTTP version is not. This method forces users in China to use the unencrypted HTTP version, which is subject to keyword filtering,” says GreatFire in a report.

The Great Firewall has taken nearly a year and a half to respond to the existence of Wikipedia’s encrypted version, which is likely because the site uses HTTP by default, GreatFire says. It is urging Wikipedia to now switch the default to HTTPS to force the Chinese government to have to make a decision on whether to fully block the site or leave Wikipedia alone.

“Based on the existing evidence, it’s more likely that GFW would leave Wikipedia alone,” says the company,  which closely monitors China’s censorship activity and other Internet issues in the country, citing examples of Gmail and Github when the government also ultimately left the sites alone.

Earlier this year, social coding site Github had been blocked by the Great Firewall of China.

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