* What's this?
-EasyPG is yet another GnuPG interface for Emacs. It consists of two
-parts: transparent file encryption utility and easy-to-use elisp
-library to interact with GnuPG.
+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
-(0) Put (require 'epg-file) in your ~/.emacs.el
+** 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.
-(1) Restart emacs
+(require 'epg-file)
-(2) C-x C-f ~/test.gpg
+** 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
-** EasyPG avoides potential security flaws of Emacs.
+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
+
+*** `call-process-region' writes data in region to temporary files
+
+`call-process-region' writes data in region to temporary files.
+EasyPG do _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.
-*** `call-process-region' writes data in region to a temporary file.
-PGG and gpg.el use `call-process-region' to communicate with a
-subprocess "gpg". So, your passphrases may leak to the filesystem.
+** GnuPG features are directly accessible from Emacs
-*** There is no way to clear strings safely.
-To prevent passphrases from been stealing from cores, `read-passwd'
-function clears passphrase strings by `(fillarray string 0)'.
-However, it is not enough. Emacs does compaction of small strings in
-GC sweep phase. If GC happens before `fillarray', passphrase strings
-may be copied elsewhere in the memory. PGG and gpg.el enables
-passphrase caching by default.
+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.