Redact sensitive information with regular expressions

Found a great idea from Zenodium.

ha-passwords.org

@@ -23,7 +23,34 @@ A literate programming version for Emacs code to generate and store passwords.
   ;;
   ;;; Code:
 #+end_src
-* Introduction
+* Overlay Redaction
+Love [[https://xenodium.com/redact-that-buffer/][this idea]] for using a regular expression to /redact/ (or at least, obscure) sensitive information before screen sharing.
+#+begin_src emacs-lisp
+  (defun toggle-redact-buffer (regexp)
+    "Redact buffer content matching regexp. A space redacts all."
+    (interactive (list (read-regexp "Text to Redact (Regexp)" 'regexp-history-last)))
+    (let* ((redacted)
+           (matches (let ((results '()))
+                      (when (string-empty-p regexp)
+                        (setq regexp "[[:graph:]]")
+                        (setq regexp-history-last regexp)
+                        (add-to-history 'regexp-history regexp))
+                      (save-excursion
+                        (goto-char (point-min))
+                        (while (re-search-forward regexp nil t)
+                          (push (cons (match-beginning 0) (match-end 0)) results)))
+                      (nreverse results))))
+      (mapc (lambda (match)
+              (dolist (overlay (overlays-in (car match) (cdr match)))
+                (setq redacted t)
+                (delete-overlay overlay))
+              (unless redacted
+                (overlay-put (make-overlay (car match) (cdr match))
+                             'display (make-string (- (cdr match) (car match)) ?x))))
+            matches)))
+#+end_src
+I’m not sure how often I will use this, so I’m not putting it on a keybinding, also so, I will also not put a name-spacing prefix on the function.
+* Password Generation
 Let's assume that I store a bunch of words in data files:
 #+begin_src emacs-lisp
   (defvar ha-passwords-data-files (list (expand-file-name "adjectives.txt"