X-Git-Url: http://git.chise.org/gitweb/?a=blobdiff_plain;f=README;h=87854fc1dd0472e86301a5ed0086c661698a93f6;hb=74b46a0ecaa2cf2e877ae29ea9f4196f812688fd;hp=b3bca3904f6a47d267d93d851bbb57c63992ead3;hpb=06b8e756e7bb432c351d70489f6b0b66b865bb27;p=elisp%2Fepg.git

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 * What's this?
 
-EasyPG is yet another GnuPG interface for Emacs.  It consists of three
-parts: transparent file encryption utility, Gnus/PGG backend, and
-easy-to-use elisp library to interact with GnuPG.
+EasyPG is yet another GnuPG interface for Emacs.  It consists of two
+parts:
+
+- "The EasyPG Assistant"
+  A GUI frontend of GnuPG
+- "The EasyPG Library"
+  A library to interact with GnuPG
 
 * Requirements
 
-** GNU Emacs 21.4 or later
+** GNU Emacs 21.4 or XEmacs 21.4
 
-** XEmacs 21.4 or later
+** GnuPG 1.4.3
 
-** GnuPG 1.4.3 or later
+* Quick start
 
-** Gnus 5.10.8 or later (optional)
+** Installation
 
-* Quick start
+  $ ./configure
+  $ sudo make install
+
+Add the following line to your ~/.emacs
+
+  (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.
 
-** Transparent file encryption
+** Passphrase may leak to a temporary file.
 
-EasyPG provides transparent file encryption similar to crypt++,
-alpaca.el, hedgehog.  To try this feature, put (require 'epg-file)
-in your ~/.emacs.el and C-x C-f ~/test.txt.gpg.
+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.
 
-** Using with Gnus/PGG
+The EasyPG Library does not use call-process-region to communicate
+with a gpg subprocess.
 
-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
+** Passphrase may be stolen from a core file.
 
-(setq pgg-scheme 'epg)
+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.
 
-* Advantages over other competitors
+The EasyPG Library dares to disable passphrase caching. Fortunately,
+there is more secure way to cache passphrases - use gpg-agent.
 
-There are many competitors of EasyPG such as Mailcrypt, PGG, gpg.el,
-etc.  EasyPG has some advantages over them.
+* MUA Integration
 
-** EasyPG avoides potential security flaws of Emacs.
+The EasyPG Library can be used in combination with MUA (Mail User
+Agents).
 
-*** `call-process-region' writes data in region to temporary files.
+** SEMI based MUA
 
-`call-process-region' writes data in region to temporary files.  PGG
-and gpg.el use `call-process-region' to communicate with a gpg
-subprocess.  Your passphrases leak to the filesystem!
+SEMI is the MIME library used by Wanderlust, cmail, T-gnus, etc.
 
-*** There is no way to clear strings safely.
+There is an EasyPG capable SEMI library called EMIKO-EasyPG.  It can
+be downloaded from the same site of the EasyPG distribution point.
 
-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.  It is recommended that as
-soon as you are done with passphrase you should clear it manually.
-However, PGG and gpg.el can keep passphrase strings in cache for a
-while and this behavior is their default!
+** PGG based MUA
 
-** GnuPG features are directly accessible from Emacs
+PGG is somewhat outdated PGP library used by Gnus, MH-E, etc.
 
-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.
+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.