Tie::EncryptedHash augments Perl hash semantics to build secure, encrypting
containers of data.  Tie::EncryptedHash introduces special hash fields that
are coupled with encrypt/decrypt routines to encrypt assignments at STORE()
and decrypt retrievals at FETCH().  By design, encrypting fields are
associated with keys that begin in single underscore.  The remaining keyspace
is used for accessing normal hash fields, which are retained without
modification.