canlock-password - hashed password (?) mysteriously in .emacs

Question

In my .emacs, this has appeared, for unknown reasons:

(custom-set-variables
  ; ...
  '(canlock-password "fdd7041be5b...")

And so on, totalling 40 characters and digits.

C-h v offers this:

canlock-password is a variable defined in `canlock.el'.
Its value is "fdd7041be5b..."

Documentation:
Password to use when signing a Cancel-Lock or a Cancel-Key header.

I use rmail and GNUS, and those use headers, other than that it doesn't remind my of anything, really, but it can of course be something unrelated that I've overlooked.

I tried to delete it, but it came back.

Answer 1

The Cancel-Lock and Cancel-Key headers are a mechanism to protect Usenet messages against cancellation by unauthorized parties. If the news server supports it, and you send a cancel message for a message that contains Cancel-Lock: foo bar, then the server only honors the cancel if the cancel message contains Cancel-key: wibble such that SHA1(wibble) = foo or SHA1(wibble) = bar.

The canlock-password is not the hash of anything, it is generated automatically by GNUS. If you don't want GNUS to change your .emacs, you need to set canlock-password yourself. canlock-password should be a randomly generated string, so you might as well let GNUS pick one. If you post from multiple places, you should use the same password everywhere. Also, don't post this value publicly; you may want to define it in a separate file.

;; in .emacs
(load-library "~/.emacs.d/passwords.el")

;; in passwords.el
(setq canlock-password "…"
      canlock-password-for-verify canlock-password)