adhoc recovery from spurious NPEs, similar quantum-effect behind 7c8ce63a3c00;
theory All_Symmetricimports Messagebegintext {* 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