For entry into China, non-Chinese citizens should apply for a visa at the Chinese Embassy or Consulate in the region they live. The simplest way is to apply for a tourist ("L") visa, which should give you enough time to attend the conference and participate in pre/post conference activities. Please contact the Embassy or Consulate in your region for specific instructions. An invitation letter is not required for obtaining a tourist visa. The regular processing time is 4 working days. Please plan ahead to allow enough time for visa processing.
More information on obtaining a tourist ("L") visa in the United States can be found here. To fill the application form Q1, you should check the Tourism box. The contact in China is Cui Lin (email@example.com).
If you have any problem on obtaining a tourist visa, please contact Cui Lin (firstname.lastname@example.org) to issue an official invitation letter to apply for a business visa. In order to obtain an invitation letter, the following conditions must be satisfied: (1) the letter will be issued only to those who had registered to the conference; (2) the person who requests the letter must fill in the request form for an invitation letter; (3) the completed request form and a copy of passport first page must be sent out to Cui Lin (email@example.com) through the email address with which the author(s) submitted their paper(s) to IEEE TrustCom-14 or its associated symposiums/workshops.