Question

From the security aspect of client/browser, connecting to a secure web site/server,

1. From the cyber security perspective, what browser features should be examined for valid certificates.
2. What are the risks of using expired web certificates

Answer 1

Part 1

Here is a very simplified explanation:

1. Your web browser downloads the web server's certificate, which contains the public key of the web server. This certificate is signed with the private key of a trusted certificate authority.

2. Your web browser comes installed with the public keys of all of the major certificate authorities. It uses this public key to verify that the web server's certificate was indeed signed by the trusted certificate authority.

3. The certificate contains the domain name and/or ip address of the web server. Your web browser confirms with the certificate authority that the address listed in the certificate is the one to which it has an open connection.

4. Your web browser generates a shared symmetric key which will be used to encrypt the HTTP traffic on this connection; this is much more efficient than using public/private key encryption for everything. Your browser encrypts the symmetric key with the public key of the web server then sends it back, thus ensuring that only the web server can decrypt it, since only the web server has its private key.

Note that the certificate authority (CA) is essential to preventing man-in-the-middle attacks. However, even an unsigned certificate will prevent someone from passively listening in on your encrypted traffic, since they have no way to gain access to your shared symmetric key.

Part 2

The following are scenarios that are most likely to follow an expired SSL certificate circumstance:

• For website-owners, expired certificates are highly capable of increasing the instances of shopping cart abandonment and a subsequent decline in sales and revenue.
• Whereas, website users put their personal information at risk by carrying out a financial transaction on a site with an expired SSL certificate.