A certificate, also known as a digital ID, provides a higher level of security with Outlook. You can use a certificate to send encrypted e-mails so that only the intended recipient can view the contents. You can also use them to sign messages to prevent tampering and prove your identity. Finally, you can use a digital ID in lieu of a username and password to access certain restricted Web sites, although this use is not relevant to Outlook.
Digital IDs are based on the technique of a public/private key pair. These are two long numbers that are related to each other. You can use either key of the pair to encrypt data, and only people who have the other key of the pair are able to unencrypt the data. When you have a digital signature, you keep your private key secret and make your public key freely available. Here’s how it works:
To send an encrypted message to people, you use their public key to encrypt it. Only they can unencrypt the message because no one else has their private key.
To prove your identity, encrypt some data using your private key. When recipients of a message decrypt the data using your public key, if the data is intact they will know that you must have encrypted it because nobody else has your private key.
Digital certificates have expiration dates, typically one year after they are issued.
If you are using Outlook at work, your employer may provide a digital ID to you that you’ll import as described ...