Reestablishing secure communication with a server after the server's certificate is renewed with a certificate authority unknown to the client

One or more non-transitory computer storage media storing computer executable instructions which when executed on a client implement a method for reestablishing secure communication with a server after verification of the server's certificate failed due to the client not having one or more certificate authority (CA) certificates that are necessary to verify the server's certificate, the method comprising:

• storing, on the client, a first server token that was received from the server;
• receiving, from the server, a current server certificate;
• attempting to verify the current server certificate;
• in response to failing to verify the current server certificate, sending, to the server, a fallback authentication request;
• in response to sending the fallback authentication request, receiving, from the server, a second server token and one or more CA certificates;
• performing fallback authentication to authenticate the server, the fallback authentication including comparing the second server token to the first server token to determine that the second server token matches the first server token;
• and
• in response to authenticating the server via the fallback authentication, adding the one or more CA certificates to a certificate store on the client.

A client comprising:

• one or more hardware processors;
• and
• computer storage media storing computer executable instructions which when executed by the one or more processors implement a method for reestablishing secure communication with a server after verification of the server's certificate failed due to the client not having one or more certificate authority (CA) certificates that are necessary to verify the server's certificate, the method comprising:
• storing, on the client, a first server token that was received from the server;
• receiving, from the server, a current server certificate;
• attempting to verify the current server certificate;
• in response to failing to verify the current server certificate, sending, to the server, a fallback authentication request;
• in response to sending the fallback authentication request, receiving, from the server, a second server token and one or more CA certificates;
• performing fallback authentication to authenticate the server, the fallback authentication including comparing the second server token to the first server token to determine that the second server token matches the first server token;
• and
• in response to authenticating the server via the fallback authentication, adding the one or more CA certificates to a certificate store on the client.