Tor network has been blocked in China. People can use the meek bridge to access the Tor network. Meek bridges make your network flow looks like the cloud computing with Microsoft or amazon , GFW is unable to differentiate the meek and the real cloud computing. And how Microsoft and amazon identify the meek? I guess that they prepared a specific RSA certificate or something like that. Tor browser uses the RSA public key to encrypt the network flow , Microsoft and amazon use the RSA secret key to decrypt the network flow. Microsoft and amazon feel very easy to identify the meek , but GFW is still unable to differentiate the meek and the real cloud computing.