put Isabelle-specifics in a "PortableIsabelle" file maintained by us;
as recommended by Joe Hurd
theory All_Symmetric
imports Message
begin
text {* All keys are symmetric *}
defs all_symmetric_def: "all_symmetric \<equiv> True"
lemma isSym_keys: "K \<in> symKeys"
by (simp add: symKeys_def all_symmetric_def invKey_symmetric)
end