X-Git-Url: http://git.chise.org/gitweb/?a=blobdiff_plain;f=README;h=30f6f0102526367247b7ec6f054b4d99d834eff4;hb=cfc87dbe5b4de5e0770c36553c6a44d4171d8bfc;hp=e231330cd6b256fdddcf68adf805ad03bd5bc6c7;hpb=3d4d9b0ed010b57ec3e9d4f8a6f15e3a55251133;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
-elisp library to interact with GnuPG.
+EasyPG is a 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.)
 
 * Requirements
 
-** GNU Emacs 21.4 or later
+** GNU Emacs 21.4 or XEmacs 21.4
 
-** XEmacs 21.4 or later
-
-** GnuPG 1.4.3 or later
-
-** Gnus 5.10.8 or later (optional)
+** 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)
+
+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 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 supports EasyPG natively, simply put the following
+line into your ~/.emacs.
+
+  (setq mml2015-use 'epg)
+
+Other options which affect on the binding are
+
+  mml2015-signers
+  mml2015-encrypt-to-self
+  mml2015-cache-passphrase
+  mml2015-passphrase-cache-expiry
+  mml2015-verbose
 
-** Transparent file encryption utility
+NOTE: You need not to install pgg-epg.el in this case.
 
-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.
+** PGG based MUA
 
-(require 'epg-file)
+PGG is somewhat outdated PGP library used by old Gnus, MH-E, etc.
 
-** Gnus/PGG backend
+There is a PGG backend using EasyPG called pgg-epg.el.  However,
+EasyPG API is a superset of PGG, so pgg-epg.el just emulates the old
+behavior of pgg.el.  Major features which PGG lacks are
 
-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.
+- Key selection user interface
+- Diagnosis interface to the verify operation
+- Web of trust
+- S/MIME using gpgsm
 
-(setq pgg-scheme 'epg)
+** SEMI based MUA
 
-* Advantages over other competitors
+SEMI is the MIME library used by Wanderlust, cmail, T-gnus, etc.
 
-There are many competitors of EasyPG such as Mailcrypt, Gnus/PGG,
-gpg.el, etc.  EasyPG has some advantages over them.
+There is an EasyPG capable SEMI library called EMIKO-EasyPG.  It can
+be downloaded from the same site of the EasyPG distribution point.
 
-** EasyPG avoides potential security flaws of Emacs
+* Security
 
-*** `call-process-region' writes data in region to temporary files
+There are security pitfalls around Emacs.
 
-`call-process-region' writes data in region to temporary files.
-EasyPG do _not_ use `call-process-region' to communicate with a gpg
-subprocess.
+** Passphrase may leak to a temporary file.
 
-*** `(fillarray string 0)' is not enough to clear passphrases
+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.
 
-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.
+The EasyPG Library does not use call-process-region to communicate
+with a gpg subprocess.
 
-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.
+** Passphrase may be stolen from a core file.
 
-** GnuPG features are directly accessible from 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.
 
-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 dares to disable passphrase caching. Fortunately,
+there is more secure way to cache passphrases - use gpg-agent.