October 20, 2008, 5:44 AM — Iâ€™ve spoken about Certificate Authorities and Certificates already. Remember that Certificates include: a public key, the owner and a digital signature. Well youâ€™ve probably asked â€œwhat is a digital signatureâ€ and how do you â€œdigitally signâ€ a certificate?
A digital signature is basically some value, a checksum. It is a data value based on a block of data and a private key. The digital signature associates the data with the owner of a specific private key. You can be confident that the person indicated as the owner of a specific private key is not an imposter. You can safely open the email you received from the â€œcertificatedâ€ owner then respond to that person, the owner, without fear or apprehension that the email will go to the wrong person. This also allows you to trust that the contents of the email were written and encrypted by the owner of the private key.
If you decrypt a message successfully with a particular public key â€“ a key that was certified by means of a digitally signed certificate â€“ then you can certain that it could have only been encrypted with the corresponding private key. Read the rest of this article>>