Based on introducing digital certificate related concepts, the paper compares the similarities and differences of digital sig-nature soft and hard certificates from the aspects of implementation process, implementation condition, convenience, security, law validi-ty, maintainability, etc.Combining with the actual status of information system, it analyzes the selection of digital signature.

Objective]To explore the metastasis regulatory of lymph node of papillary thyroid cancer and to analyze the influence factors.[Methods]Clinical data of 375 papillary thyroid cancer patients at our hospital between Jun 2011 and Sep 2015 were retrospectively reviewed and summarized the metastasis regulatory of lymph nodes and the tumor characteristics.[Results]All selected patients were diagnosed papillary thyroid cancer. The Total metastasis rate of cervical lymph node was 67.47%,the metastasis rate of region Ⅵ lymph nodes was 64.27%;the metastasis rate of region Ⅱ~Ⅴ lymph nodes was 36.53%. The metastasis rate of lymph nodes of the patients with tumor diameter over 1 cm,breaking through thyroid membrane and invading the cervical muscle were significantly increased(P < 0.05).[Conclusion]The central group lymph nodes were the most metastasis region of papillary thyroid cancer and should routinely be dissected by the first time of surgery. When the tumor diameter greater than 1 cm or cancer breakthrough thyroid membrane and/or invading the cervical muscles ,the ipsilateral lateral neck lymph nodes should be dissected at the same time.