Wilde was able to find that the method the firewall was using to identify which sessions to go after had something to do with the list of SSL ciphers contained in the SSL packet the client sends at the beginning of a session. By changing that list, he was able to evade the blocking of the Chinese firewall. More long-term solutions are in the works, as well, including password protection for bridge relays and the establishment of another layer on top of the session that simply looks like binary data.

via How the Great Firewall of China Blocks Tor | threatpost.