Fixed.

[elisp/epg.git] / README

diff --git a/README b/README
index 610523f..87854fc 100644 (file)
--- a/README
+++ b/README
@@ -1,11 +1,12 @@
 * 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:
 
-- "The EasyPG Assistant" which provides basic GUI of GnuPG
-- "The EasyPG Library" which enables use of various features of GnuPG
-
-NOTE: EasyPG is neither a fork nor a re-implementation of Gnus/PGG.
+- "The EasyPG Assistant"
+  A GUI frontend of GnuPG
+- "The EasyPG Library"
+  A library to interact with GnuPG
 
 * Requirements
 
@@ -24,31 +25,55 @@ Add the following line to your ~/.emacs
 
   (require 'epa-setup)
 
-Then you can browse your keyring by M-x epa-list-keys.  In addition,
+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 epg-dired-do-encrypt)
+  : e (or M-x epa-dired-do-encrypt)
   (select recipients and click [OK])
 
-* Security consideration
+* 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.
+
+The EasyPG Library does not use call-process-region to communicate
+with a gpg subprocess.
+
+** Passphrase may be stolen from a core file.
+
+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.
+
+The EasyPG Library dares to disable passphrase caching. Fortunately,
+there is more secure way to cache passphrases - use gpg-agent.
+
+* MUA Integration
+
+The EasyPG Library can be used in combination with MUA (Mail User
+Agents).
+
+** 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 crashes 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 to disable passphrase caching.  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.