This section describes certificate and certificate chain. A certificate contains someone's public key signed by a trusted authority.
What is Certificate: A certificate is digitally signed statement from the issuer saying
that the public key of the subject has some specific value.
The above definition is copied from the JDK 1.3.1 documentation. It has
a couple of important terms:
"signed statement" - The certificate must be signed by the issuer with
a digital signature.
"issuer" - The person or organization who is issuing this certificate.
"public key" - The public key of a key pair selected by the subject.
"subject" - The person or organization who owns the public key.
X.509 Certificate - A certificate written in X.509 standard format.
X.509 standard was introduction in 1988. It requires a certificate to have
the following information:
Version - X.509 standard version number.
Serial Number - A sequence number given to each certificate.
Signature Algorithm Identifier - Name of the algorithm used
to sign this certificate by the issuer
Issuer Name - Name of the issuer.
Validity Period - Period during which this certificate is valid.
Subject Name - Name of the owner of the public key.
Subject Public Key Information - The public key and its related information.
How can you get a certificate for your own public key?
Requesting it from a Certificate Authority (CA), like VeriSign, Thawte or Entrust.
Doing it yourself - using tools like JDK "keytool" to generate a self-signed certificate.
What is Certificate Chain: A certificate chain is a series of certificates that one certificate signs the
public key of the issuer of the next certificate. Usually the top certificate
(the first certificate) is self-signed, where issuer signed its own public key.
