X-Git-Url: http://git.chise.org/gitweb/?a=blobdiff_plain;f=README;h=87854fc1dd0472e86301a5ed0086c661698a93f6;hb=74b46a0ecaa2cf2e877ae29ea9f4196f812688fd;hp=64700a6e4e2def128501b0ebe2d1ed39f075c6ac;hpb=7f1f6fca222a32fc153ffddfc180d3d0855c2650;p=elisp%2Fepg.git

diff --git a/README b/README
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+++ b/README
@@ -1,63 +1,79 @@
 * What's this?
 
-EasyPG is yet another GnuPG interface for Emacs.  It consists of two parts:
+EasyPG is yet another GnuPG interface for Emacs.  It consists of two
+parts:
 
-epa.el - EasyPG Assistant, a basic GUI of GnuPG
-epg.el - the EasyPG library which interacts with GnuPG
-
-NOTE: EasyPG is not a fork or a re-implementation of Gnus/PGG.
+- "The EasyPG Assistant"
+  A GUI frontend of GnuPG
+- "The EasyPG Library"
+  A library to interact with GnuPG
 
 * Requirements
 
-** GNU Emacs 21.4 or later, XEmacs 21.4 or later
+** GNU Emacs 21.4 or XEmacs 21.4
 
-** GnuPG 1.4.3 or later
+** GnuPG 1.4.3
 
 * Quick start
 
 ** Installation
 
-$ ./configure
-$ sudo make install
+  $ ./configure
+  $ sudo make install
 
 Add the following line to your ~/.emacs
 
-(require 'epa-setup)
+  (require 'epa-setup)
+
+Then you can browse your keyring by `M-x epa-list-keys'.  In addition,
+you can do some cryptographic operations on dired.
+
+  M-x dired
+  (mark some files)
+  : e (or M-x epa-dired-do-encrypt)
+  (select recipients and click [OK])
+
+* Security
+
+There are security pitfalls around Emacs.
+
+** Passphrase may leak to a temporary file.
+
+The function call-process-region writes data in region to a temporary
+file. If your PGP library used this function, your passphrases would
+leak to the filesystem.
 
-* Advantages over other competitors
+The EasyPG Library does not use call-process-region to communicate
+with a gpg subprocess.
 
-There are many competitors of EasyPG such as Mailcrypt, Gnus/PGG,
-gpg.el, etc.  EasyPG has some advantages over them.
+** Passphrase may be stolen from a core file.
 
-** EasyPG avoides potential security flaws of Emacs
+If Emacs crashes and dumps core, Lisp strings in memory are also
+dumped within the core file. read-passwd function clears passphrase
+strings by (fillarray string 0) to avoid this risk. However, Emacs
+performs compaction in gc_sweep phase. If GC happens before fillarray,
+passphrase strings may be moved elsewhere in memory. Therefore,
+passphrase caching in elisp is generally a bad idea.
 
-See "Security consideration" section.
+The EasyPG Library dares to disable passphrase caching. Fortunately,
+there is more secure way to cache passphrases - use gpg-agent.
 
-** GnuPG features are directly accessible from Emacs
+* MUA Integration
 
-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.
+The EasyPG Library can be used in combination with MUA (Mail User
+Agents).
 
-* Security consideration
+** SEMI based MUA
 
-** `call-process-region' writes data in region to a temporary file
+SEMI is the MIME library used by Wanderlust, cmail, T-gnus, etc.
 
-`call-process-region' writes data in region to a temporary file.
-EasyPG does *not* use `call-process-region' to communicate with a gpg
-subprocess.
+There is an EasyPG capable SEMI library called EMIKO-EasyPG.  It can
+be downloaded from the same site of the EasyPG distribution point.
 
-** `(fillarray string 0)' is not enough to clear passphrases
+** PGG based MUA
 
-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.
+PGG is somewhat outdated PGP library used by Gnus, MH-E, etc.
 
-Fortunately, there is gpg-agent to cache passphrases in more secure
-way, so the EasyPG library dares *not* to cache passphrase by itself.
-Elisp programs can set `epg-context-passphrase-callback' to cache
-user's passphrases.
+There is a PGG backend using EasyPG called pgg-epg.el.  However,
+pgg-epg.el provides no more additional features than pgg-gpg.el,
+because PGG's API is restricted so that it supports old PGP 2.x/5.x.