Mona: Secure Multi-Owner Data Sharing for Dynamic Groups

Question

Could you spare some time to help me with a small problem? I need to explain

 

I don't know how generate this code wCHCQycUzVJbq2kaxaA0cKGD0IpYfyiv3/F/B1KMcwI= from sql server and Microsoft Visual Studio ASP.net by groups for signature generation .

 

If someone has information, I can contact him and give him the complete project if possible.