WeChat:
據說
A (encryption) => WeCha Server => decryption => Censorship => encryption => B (decryption)
如果A and B都不在牆內，那麽 Censorship 這一步沒有
Signal:
A (encryption) => Signal Server => B (decryption)
Skype:
牆外下載的軟件，有 end-to-end encryption 選擇，但是不支持 audio/video encryption
牆內下載的軟件，據說沒有end-to-end encryption 選擇，所以與 WeChat 私密性差不多
