The name of the associated key-pair from a key-pair
table. If a key-pair is not yet associated, the value
of this object will be a zero length string.
If a key-pair is already associated, it can be modified
only if the identity certificate is absent as indicated
by a non-zero length string value of the object
cpkiIssuerCertFileName. This is because of the fact that
the identity certificate is certifying this key-pair.