here is a list of effected classes.
if there is no comment with a particular class/operation,
investigate whether the synchronization is unnecessary.
otherwise, investigate the comment.

--------------------------------------------------------

java.security.CodeSource

java.security.GuardedObject
  - should writeObject synchronize on 'object' instead?

java.security.UnresolvedPermission

javax.security.auth.Subject.SecureSet
  - should writeObject synchronize around iteration instead?

javax.security.auth.kerberos.KerberosPrincipal

javax.security.auth.kerberos.KeyImpl
- synchronize destroy and writeObject operation?

javax.security.auth.kerberos.ServicePermission

sun.security.pkcs.PKCS8Key

sun.security.provider.IdentityDatabase
- need to synchronize data in class with writeObject (do we care?)

sun.security.x509.X509Cert
- check whether cert contents can mutate during writeObject

sun.security.x509.X509Key