X-Git-Url: http://git.chise.org/gitweb/?a=blobdiff_plain;f=README;h=e231330cd6b256fdddcf68adf805ad03bd5bc6c7;hb=95ff40c9179c88308fe96e1adb0ef220b67f265c;hp=f9466ca305ea3a0f507fe1c8db94a654ccdd8bf8;hpb=a1e7cd13bfc9fa14fb80be961892d727ed4bd347;p=elisp%2Fepg.git

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 * What's this?
 
-EasyPG is yet another GnuPG interface for Emacs.  It consists of a
-transparent file encryption application 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.