eliminated Plain_HOLCF.thy (see also 8e92772bc0e8): it was modeled after HOL/Plain.thy which was discontinued later;
theory All_Symmetric
imports Message
begin
text \<open>All keys are symmetric\<close>
overloading all_symmetric \<equiv> all_symmetric
begin
definition "all_symmetric \<equiv> True"
end
lemma isSym_keys: "K \<in> symKeys"
by (simp add: symKeys_def all_symmetric_def invKey_symmetric)
end