+(defun mml2015-epg-find-usable-key (keys usage)
+ (catch 'found
+ (while keys
+ (let ((pointer (epg-key-sub-key-list (car keys))))
+ (while pointer
+ (if (and (memq usage (epg-sub-key-capability (car pointer)))
+ (not (memq (epg-sub-key-validity (car pointer))
+ '(revoked expired))))
+ (throw 'found (car keys)))
+ (setq pointer (cdr pointer))))
+ (setq keys (cdr keys)))))
+