This may be the SSL certificate, service communication certificate, token decryption or token signing certificates.
A certificate securely binds a public key to the entity that holds the corresponding private key.This is because certificate revocation information is crucial for a user’s application that is seeking to verify that a particular certificate is currently (not just formerly) considered trustworthy.Certificate revocation information is often stored in the form of a certificate revocation list, although this is not the only form it can take.Digitally signing a message applies the sender's certificate and public key to the message.Your certificate is sent with the message to help authenticate you to the recipient. After you add or import the certificate to your contact list, Outlook can use it to verify digitally signed mail from the contact.Microsoft Outlook uses certificates in cryptographic e-mail messaging to help provide more secure communications.
To use cryptography when you send and receive e-mail messages, you must first obtain a digital ID from a certificate authority (CA).
The disconnected connections must be reconnected by the end user.
The disconnected connections can be reconnected automatically depending on the client software used.
With certificates, host computers on the Internet no longer have to maintain a set of passwords for individual subjects who need to be authenticated as a prerequisite to access.
Instead, the host merely establishes trust in a certification authority that certifies individuals and resources that hold private keys.
Active Directory Federation Services (AD FS) heavily leverages X.509 certificates to allow the solution to function securely.