X-Git-Url: http://git.chise.org/gitweb/?a=blobdiff_plain;f=README;h=3c13257560799f84c763dd848476ceabd9bc6852;hb=116cf83f4957f12852882e9f5aef8766cbee3711;hp=5c06cd0aa5a57a24b652a415e4855929bddbe5a3;hpb=7e17a8f25936fb35e23606f5c54bde52f7a8160f;p=elisp%2Fepg.git

diff --git a/README b/README
index 5c06cd0..3c13257 100644
--- a/README
+++ b/README
@@ -1,17 +1,33 @@
 * What's this?
 
-EasyPG is yet another GnuPG interface for Emacs.  It consists of two parts:
+EasyPG is an all-in-one GnuPG interface for Emacs.  It has two
+aspects: convenient tools which allow to use GnuPG from Emacs (EasyPG
+Assistant), and a fully functional interface library to GnuPG (EasyPG
+Library).
 
-- "The EasyPG Assistant" which provides basic GUI of GnuPG
-- "The EasyPG Library" which enables use of various features of GnuPG
+* Features
 
-NOTE: EasyPG is not a fork or a re-implementation of Gnus/PGG.
+The EasyPG Assistant provides the following features:
+
+- Keyring browser.
+- Cryptographic operations on regions.
+- Cryptographic operations on files.
+- Dired integration.
+- Encryption/decryption of *.gpg files.
+
+The EasyPG Library provides the following features:
+
+- The API covers most functions of GnuPG like GPGME.
+- S/MIME support using gpgsm.
+- Designed to avoid potential security pitfalls around Emacs
 
 * Requirements
 
-** GNU Emacs 21.4 or later, XEmacs 21.4 or later
+** GNU Emacs 21.4, XEmacs 21.4, or later
 
 ** GnuPG 1.4.3 or later
+   If you are using earlier versions, you will need to specify
+   --disable-gpg-test when ./configure.
 
 * Quick start
 
@@ -24,30 +40,86 @@ Add the following line to your ~/.emacs
 
   (require 'epa-setup)
 
-Then you can do some cryptographic operations on dired.
+Restart emacs and type `M-x epa- TAB', and you will see a lot of
+commands available.  For example,
+
+- To browse your keyring, type `M-x epa-list-keys'
+- To create a cleartext signature of the region, type `M-x epa-sign-region'
+
+You can also do some cryptographic operations from dired.
 
   M-x dired
   (mark some files)
-  : e (or M-x epg-dired-do-encrypt)
-  (select recipients and click [OK])
+  : e (or M-x epa-dired-do-encrypt)
+  (select recipients by 'm' and click [OK])
+
+* MUA Integration
+
+The EasyPG Library can be used in combination with various MUA (Mail
+User Agents).
+
+** CVS version of Gnus
+
+CVS version of Gnus uses EasyPG by default.  To make sure of that,
+check mml2015-use set to 'epg.  Other options which affect on the
+EasyPG are
+
+  mml2015-signers
+  mml2015-encrypt-to-self
+  mml2015-cache-passphrase
+  mml2015-passphrase-cache-expiry
+  mml2015-verbose
+
+NOTE: You don't need pgg-epg.el in this case.
+
+** PGG based MUA
+
+PGG is outdated PGP library used by old Gnus (<= v5.11), MH-E, etc.
+
+There is a PGG backend written using EasyPG called pgg-epg.el.
+However, EasyPG API is a superset of PGG and pgg-epg.el provides
+nothing but compatibility with PGG.
+
+*** Limitations of PGG
+
+As I noted "PGG is outdated PGP library" above, PGG has several
+limitations.  For example
+
+- PGG can't handle a message signed with multiple keys.
+- PGG can't prompt a user which key is being used.
+- PGG can't create a binary PGP messages.
+- PGG doesn't provide a way to select keys per cryptographic operation.
+- PGG ignores GnuPG's trust metrics.
+
+** SEMI based MUA
+
+SEMI is the MIME library used by Wanderlust, cmail, T-gnus, etc.
+
+There is an EasyPG capable SEMI library called EMIKO-EasyPG.  It can
+be downloaded from the same site of the EasyPG distribution point.
+
+* Security
+
+There are security pitfalls around Emacs.  EasyPG is written with
+avoiding them.
 
-* Security consideration
+** Passphrase may leak to a temporary file.
 
-** `call-process-region' writes data in region 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.
 
-`call-process-region' writes data in region to a temporary file.
-EasyPG does *not* use `call-process-region' to communicate with a gpg
-subprocess.
+The EasyPG Library does not use call-process-region to communicate
+with a gpg subprocess.
 
-** `(fillarray string 0)' is not enough to clear passphrases
+** Passphrase may be stolen from a core file.
 
-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.
+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.
 
-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.
+The EasyPG Library dares to disable passphrase caching. Fortunately,
+there is more secure way to cache passphrases - use gpg-agent.