Explaining how VPN encryption works is quite similar to how Bitcoin works at its core. The RSA key associated with the VPN connection encryption operates similarly to a lock.Using the Internet in China has always been a bit of a struggle, simply because the government is very restrictive regarding which content can be accessed by residents. To counter this problem, many Chinese Internet users have signed up for VPN services to bypass the Great Firewall. But as it turns out, even those services are not free from government surveillance, as their lackluster encryption tools are relatively weak.Chinese VPN Providers Use Weak Encryption
One of the main reasons people use VPN providers is because these services will encrypt all Internet traffic. Doing so will keep all of the information gathered during a browsing session safe from prying eyes. Furthermore, governments, such as the Chinese officials, are unable to block Internet pages from being accessed when using such a VPN service.
However, as it turns out, several Chinese VPN providers are not using proper encryption, resulting in government officials being able to access user data in the end. What makes things even worse is how the popular commercial VPN providers are using this weaker form of encryption. Needless to say, this is a great cause for concern, especially in China.
ExpressVPN and Astrill – both of whom are quite popular VPN providers in China – are using 1024-bit RSA key to encrypt all connections. While this may sound like a proper security measure to people who are not as tech-savvy, this form of encryption can be bypassed without much trouble. That is, as far as the Chinese government goes at least.
By using less-than-optimal encryption, both VPN providers are wide open to having government officials snoop around whenever data is collected. While there is no real evidence documenting this to be the case, hardly anyone would be surprised if the Chinese government was, in fact, accessing data collected by both ExpressVPN and Astrill.
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http://www.newsbtc.com/2016/01/25/popular-chinese-vpn-providers-can-learn-from-bitcoins-encryption-methods/