This class represents an X.500 Principal.
X500Principals are represented by distinguished names such as
"CN=Duke, OU=JavaSoft, O=Sun Microsystems, C=US".

 This class can be instantiated by using a string representation
of the distinguished name, or by using the ASN.1 DER encoded byte
representation of the distinguished name.  The current specification
for the string representation of a distinguished name is defined in
RFC 2253: Lightweight
Directory Access Protocol (v3): UTF-8 String Representation of
Distinguished Names. This class, however, accepts string formats from
both RFC 2253 and RFC 1779:
A String Representation of Distinguished Names, and also recognizes
attribute type keywords whose OIDs (Object Identifiers) are defined in
RFC 3280: Internet X.509
Public Key Infrastructure Certificate and CRL Profile.

 The string representation for this X500Principal
can be obtained by calling the getName methods.

 Note that the getSubjectX500Principal and
getIssuerX500Principal methods of
X509Certificate return X500Principals representing the
issuer and subject fields of the certificate.

 This class represents an X500PrivateCredential.
It associates an X.509 certificate, corresponding private key and the
KeyStore alias used to reference that exact key pair in the KeyStore.
This enables looking up the private credentials for an X.500 principal
in a subject.