how do I pass variables between web sites in asp.net

option 1:
Pass the data as a POST from website A to website B, that way you do not need to encrypt or it is visible in the query string.

option 2:
Insert the data in the database from website A and let website B page access that data from the database (provided both have access to the same database)

option 3:
use query string with digital signature (encryption).