Re: encrypt.el in No Gnus 0.7

[Ted Zlatanov <tzz@lifelogs.com>]

On Mon, 05 Nov 2007 03:47:04 -0500 Richard Stallman <rms@gnu.org> wrote: 

RS> I just looked at encrypt.el.  It appears to support just GnuPG
RS> and "Built-in simple XOR".  And built-in simple XOR is just an
RS> example, not for real use.

RS>     The idea is to allow users to supply their own ciphers, and to support
RS>     other external utilities as users find it necessary.

RS> It is a sensible feature, but is it worth including in Emacs?  I am
RS> not convinced this is sufficiently useful to be worth including.

In my experience, giving users creative freedom is always worth it.
Emacs is built around the idea of letting users do what they want, isn't
it?  I am surprised you are OK with locking Emacs users into GnuPG,
which is nice software but certainly not the only way to do encryption.

RS> Is there any sign that users use it?

The package was in Gnus, and I don't have bug reports.  I have not
advertised the library so far, except for brief notes to Gnus users.  So
I don't have a sample big enough to answer your question.

RS>     1) users don't have to install GnuPG to use simple obfuscation ciphers
RS>     (yes, this is sometimes useful).

RS> If you mean Rot13, aren't there other interfaces for that?  It seems
RS> to me that we don't want to use the same command for Rot13 as we use
RS> for GPG, because it is inconvenient to have to select one or the other
RS> each time.  We want two different commands.

I don't mean ROT13 specifically.  I keep repeating this: the users will
come up with interesting ciphers.  Instead of anticipating their needs,
the API should support them by being simple and flexible.

In any case, the user wouldn't select a cipher each time.  The
encrypt-find-model function will determine the encryption model,
currently from an alist.  The user chooses, for example, that
~/.authinfo is encrypted with GnuPG, but ~/emacs/*.el will use cipher X
because it's more appropriate.  Perhaps cipher X is the XOR cipher
because the user is OK with simple obfuscation.

RS>     3) other external utilities can be supported.

RS> Are there any that are useful to support?

I found a few GPL ones (just a sample list) with a simple web search:

MCrypt http://mcrypt.sourceforge.net/
AxCrypt http://www.axantum.com/AxCrypt/
ScramDisk 4 Linux http://sourceforge.net/projects/sd4l/
Several steganography tools (hide data inside an image, for example)

They all do things GnuPG doesn't as far as I can tell, though some
functionality may overlap.

RS>     4) ciphers, being Emacs Lisp code, can do almost anything: SSH to a
RS>     remote machine, use BBDB, use IMAP, use version control...

RS> I really don't like the idea of labeling such things as "encryption".

External functions may be involved in customizing the encryption process
Here are some examples (again, I'd rather let the users implement what
they need, this is just my list of things I might find interesting):

- use BBDB to store shared keys or public keys

- get shared or public keys from an IMAP server (stored in a message)

- on a CVS/SVN/etc. checkin/checkout, use another file in the repository
  to modify the shared key or as the shared key

- pure Lisp ciphers for quick experimentation and sharing

Ted