* What's this?

EasyPG is yet another GnuPG interface for Emacs.  It consists of three
parts: transparent file encryption utility, Gnus/PGG backend, and
elisp library to interact with GnuPG.

* Requirements

** GNU Emacs 21.4 or later, XEmacs 21.4 or later

** GnuPG 1.4.3 or later

** Gnus 5.10.8 or later (optional)

* Quick start

** Installation

$ ./configure
$ sudo make install

** Transparent file encryption utility

EasyPG provides transparent file encryption utility similar to
crypt++, alpaca.el, hedgehog.  To try this, add the following line to
your ~/.emacs and C-x C-f ~/test.txt.gpg.

(require 'epf)

** Gnus/PGG backend

EasyPG provides an implementation of the backend interface of
Gnus/PGG.  To use EasyPG instead of pgg-gpg, install pgg-epg.el and
add the following line to your ~/.gnus.

(setq pgg-scheme 'epg)

* Advantages over other competitors

There are many competitors of EasyPG such as Mailcrypt, Gnus/PGG,
gpg.el, etc.  EasyPG has some advantages over them.

** EasyPG avoides potential security flaws of Emacs

See "Security consideration" section.

** GnuPG features are directly accessible from Emacs

Other competitors provide only specific features of GnuPG since they
still support PGP 2.*, 5.*, 6.*.  As the name indicates, EasyPG is
inspired by GPGME (GnuPG Made Easy), and the library interface is
close to GPGME.  With EasyPG you can benefit from a lot of features of
GnuPG.

* Security consideration

** `call-process-region' writes data in region to a temporary file

`call-process-region' writes data in region to a temporary file.
EasyPG does *not* use `call-process-region' to communicate with a gpg
subprocess.

** `(fillarray string 0)' is not enough to clear passphrases

If Emacs crashed and dumps core, passphrase strings in memory are also
dumped within the core file.  `read-passwd' function clears passphrase
strings by `(fillarray string 0)'.  However, Emacs performs compaction
in gc_sweep phase.  If GC happens before `fillarray', passphrase
strings may be moved elsewhere in memory.

Fortunately, there is gpg-agent to cache passphrases in more secure
way, so EasyPG dares *not* to cache passphrase.  Elisp programs can
set `epg-context-passphrase-callback' to cache user's passphrases.