I want to have two servers, Server A and Server B. Server A does all the authentication (username and password). If the user is authenticated at Server A, then Server A will send POST data of a session id, ip address, useragent, etc. of the user. Server B will receive all this data over SSL and will trust Server A and give access to the user. Also, Server B will only accept POST data from Server A by means of Server A's IP.
My question is, since the post data is sent over curl/ssl, can it be intercepted or stolen while in traffic? can the hacker view the session id in plain text(the most important component here)?
Is there anything I can do to increase the security of this method?