A Digital certificate is carrier of a person or entity’s Public Key, it contains public key and some information about it like meta data. It establishes your credentials when doing business or other transactions on the Web. In simple words Digital Certificate is the attachment to an electronic message used for security purposes. The common use of a digital certificate is to verify that a user sending a message is who it claims to be, and to provide the receiver with the means to encode a reply.

Digital Certificate provides a means of proving your identity in electronic transactions; just like a passport. It can be presented electronically to prove your identity or your right to access information or services on-line. A Digital Certificate is issued by a Certification Authority (CA) and signed with the CA's private key. It typically contains the:

• Serial number of the Digital Certificate
• Owner's name
• Owner's public key
• Name of the issuer (the CA that issued the Digital Certificate)
• Digital signature of the issuer so that a recipient can verify that the certificate is real.
• Expiry date of the public key.
• Other extensions.

Above information is contained in a digital certificate. Most widely accepted format for digital certificates is defined by the CCITT X.509 international standard. And the most widely used standard for digital certificates is X.509. It has three versions V1, v2 and V3, X509 V1 and V3 are more used where V1 certificates are mostly CA certificates, V3 certificates can have extensions. Once a PDF document is signed, the digital signature also contains the certificate of the signing entity and this is used for verification purpose when the document is opened using a PDF reader like Adobe PDF Reader. Test sign a PDF file, click here.