\input texinfo                  @c -*- mode: texinfo -*-
@c %**start of header
@setfilename ../../info/epa.info
@settitle EasyPG Assistant User's Manual
@include docstyle.texi
@c %**end of header

@set VERSION 1.0.0

@copying
This file describes EasyPG Assistant @value{VERSION}.

Copyright @copyright{} 2007--2023 Free Software Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover Texts being ``A GNU Manual,''
and with the Back-Cover Texts as in (a) below.  A copy of the license
is included in the section entitled ``GNU Free Documentation License''.

(a) The FSF's Back-Cover Text is: ``You have the freedom to copy and
modify this GNU manual.''
@end quotation
@end copying

@dircategory Emacs misc features
@direntry
* EasyPG Assistant: (epa).      An Emacs user interface to GNU Privacy Guard.
@end direntry

@titlepage
@title EasyPG Assistant

@author by Daiki Ueno
@page

@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents

@node Top
@top EasyPG Assistant user's manual

EasyPG Assistant is an Emacs user interface to GNU Privacy Guard
(GnuPG, @pxref{Top, , Top, gnupg, Using the GNU Privacy Guard}).

EasyPG Assistant is a part of the package called EasyPG, an all-in-one
GnuPG interface for Emacs.  EasyPG also contains the library interface
called EasyPG Library.

@ifnottex
@insertcopying
@end ifnottex

@menu
* Overview::
* Quick start::
* Commands::
* GnuPG version compatibility::
* GnuPG Pinentry::
* Caching Passphrases::
* Bug Reports::
* GNU Free Documentation License::  The license for this documentation.
* Key Index::
* Function Index::
* Variable Index::
@end menu

@node Overview
@chapter Overview

EasyPG Assistant is an Emacs frontend application to @acronym{GnuPG,
GNU Privacy Guard} that provides the following features:

@itemize @bullet
@item Key management.
@item Cryptographic operations on regions.
@item Cryptographic operations on files.
@item Dired integration.
@item Mail-mode integration.
@item Automatic encryption/decryption of *.gpg files.
@end itemize

@node Quick start
@chapter Quick start

You can use EasyPG Assistant without any Emacs or GnuPG configuration
whatsoever, for example to encrypt and decrypt files automatically
with symmetric encryption, @xref{Encrypting/decrypting gpg files}.
However, to use the full set of EasyPG Assistant's functions you
should have at least some minimum GnuPG configuration in place.

John Michael Ashley's GNU Privacy Handbook, available online as part
of @url{https://gnupg.org/documentation/guides.html, the GnuPG user
guides}, provides an introduction to GnuPG use and configuration.

EasyPG Assistant commands are prefixed by @samp{epa-}.  For example,

@itemize @bullet
@item To browse your keyring, type @kbd{M-x epa-list-keys}

@item To create a cleartext signature of the region, type @kbd{M-x epa-sign-region}

@item To encrypt a file, type @kbd{M-x epa-encrypt-file}

@item To query a key server for keys, type @kbd{M-x epa-search-keys}
@end itemize

EasyPG Assistant provides several cryptographic features which can be
integrated into other Emacs functionalities.  For example, automatic
encryption/decryption of @file{*.gpg} files.

@node Commands
@chapter Commands

This chapter introduces various commands for typical use cases.

@menu
* Key management::
* Cryptographic operations on regions::
* Cryptographic operations on files::
* Dired integration::
* Mail-mode integration::
* Encrypting/decrypting gpg files::
* Querying a key server::
@end menu

@node Key management
@section Key management
Probably the first step of using EasyPG Assistant is to browse your
keyring.  @kbd{M-x epa-list-keys} is corresponding to @samp{gpg
--list-keys} from the command line.

@deffn Command epa-list-keys name mode
Show all keys matched with @var{name} from the public keyring.
@end deffn

@noindent
The output looks as follows.

@example
  u A5B6B2D4B15813FE Daiki Ueno <ueno@@unixuser.org>
@end example

@noindent
A character on the leftmost column indicates the trust level of the
key.  If it is @samp{u}, the key is marked as ultimately trusted.  The
second column is the key ID, and the rest is the user ID.

You can move over entries by @key{TAB}.  If you type @key{RET} or
click button1 on an entry, you will see more detailed information
about the key you selected.

@example
 u Daiki Ueno <ueno@@unixuser.org>
 u A5B6B2D4B15813FE 1024bits DSA
        Created: 2001-10-09
        Expires: 2007-09-04
        Capabilities: sign certify
        Fingerprint: 8003 7CD0 0F1A 9400 03CA  50AA A5B6 B2D4 B158 13FE
 u 4447461B2A9BEA2D 2048bits ELGAMAL_E
        Created: 2001-10-09
        Expires: 2007-09-04
        Capabilities: encrypt
        Fingerprint: 9003 D76B 73B7 4A8A E588  10AF 4447 461B 2A9B EA2D
@end example

@noindent
To browse your private keyring, use @kbd{M-x epa-list-secret-keys}.

@deffn Command epa-list-secret-keys name
Show all keys matched with @var{name} from the private keyring.
@end deffn

@noindent
In @file{*Keys*} buffer, several commands are available.  The common
use case is to export some keys to a file.  To do that, type @kbd{m}
to select keys, type @kbd{o}, and then supply the filename.

Below are other commands related to key management.  Some of them take
a file as input/output, and others take the current region.

@deffn Command epa-insert-keys keys
Insert selected @var{keys} after the point.  It will let you select
keys before insertion.  By default, it will encode keys in the OpenPGP
armor format.
@end deffn

@deffn Command epa-import-keys file
Import keys from @var{file} to your keyring.
@end deffn

@deffn Command epa-import-keys-region start end
Import keys from the current region between @var{start} and @var{end}
to your keyring.
@end deffn

@deffn Command epa-import-armor-in-region start end
Import keys in the OpenPGP armor format in the current region between
@var{start} and @var{end}.  The difference from
@code{epa-import-keys-region} is that
@code{epa-import-armor-in-region} searches armors in the region and
applies @code{epa-import-keys-region} to each of them.
@end deffn

@deffn Command epa-delete-keys allow-secret
Delete selected keys.  If @var{allow-secret} is non-@code{nil}, it
also delete the secret keys.
@end deffn

@node Cryptographic operations on regions
@section Cryptographic operations on regions

@deffn Command epa-decrypt-region start end
Decrypt the current region between @var{start} and @var{end}.  It
replaces the region with the decrypted text.
@end deffn

@deffn Command epa-decrypt-armor-in-region start end
Decrypt OpenPGP armors in the current region between @var{start} and
@var{end}.  The difference from @code{epa-decrypt-region} is that
@code{epa-decrypt-armor-in-region} searches armors in the region
and applies @code{epa-decrypt-region} to each of them.  That is, this
command does not alter the original text around armors.
@end deffn

@deffn Command epa-verify-region start end
Verify the current region between @var{start} and @var{end}.  It sends
the verification result to the minibuffer or a popup window.  It
replaces the region with the signed text.
@end deffn

@deffn Command epa-verify-cleartext-in-region
Verify OpenPGP cleartext blocks in the current region between
@var{start} and @var{end}.  The difference from
@code{epa-verify-region} is that @code{epa-verify-cleartext-in-region}
searches OpenPGP cleartext blocks in the region and applies
@code{epa-verify-region} to each of them.  That is, this command does
not alter the original text around OpenPGP cleartext blocks.
@end deffn

@deffn Command epa-sign-region start end signers type
Sign the current region between @var{start} and @var{end}.  By
default, it creates a cleartext signature.  If a prefix argument is
given, it will let you select signing keys, and then a signature
type.
@end deffn

@deffn Command epa-encrypt-region start end recipients sign signers
Encrypt the current region between @var{start} and @var{end}.  It will
let you select recipients.  If a prefix argument is given, it will
also ask you whether or not to sign the text before encryption and if
you answered yes, it will let you select the signing keys.
@end deffn

@node Cryptographic operations on files
@section Cryptographic operations on files

@deffn Command epa-decrypt-file file &optional output
Decrypt @var{file}.  If you do not specify the name @var{output} to
use for the decrypted file, this function prompts for the value to use.
@end deffn

@deffn Command epa-verify-file file
Verify @var{file}.
@end deffn

@deffn Command epa-sign-file file signers type
Sign @var{file}.  If a prefix argument is given, it will let you
select signing keys, and then a signature type.
@end deffn

@deffn Command epa-encrypt-file file recipients
Encrypt @var{file}.  It will let you select recipients.
@end deffn

@node Dired integration
@section Dired integration

EasyPG Assistant extends Dired Mode for GNU Emacs to allow users to
easily do cryptographic operations on files.  For example,

@example
M-x dired
(mark some files)
: e (or M-x epa-dired-do-encrypt)
(select recipients by 'm' and click [OK])
@end example

@noindent
The following keys are assigned.

@table @kbd
@item : d
@kindex : d
@findex epa-dired-do-decrypt
Decrypt marked files.

@item : v
@kindex : v
@findex epa-dired-do-verify
Verify marked files.

@item : s
@kindex : s
@findex epa-dired-do-sign
Sign marked files.

@item : e
@kindex : e
@findex epa-dired-do-encrypt
Encrypt marked files.

@end table

@node Mail-mode integration
@section Mail-mode integration

EasyPG Assistant provides a minor mode @code{epa-mail-mode} to help
user compose inline OpenPGP messages.  Inline OpenPGP is a traditional
style of sending signed/encrypted emails by embedding raw OpenPGP
blobs inside a message body, not using modern MIME format.

NOTE: Inline OpenPGP is not recommended and you should consider to use
PGP/MIME@.  See
@uref{https://josefsson.org/inline-openpgp-considered-harmful.html,
Inline OpenPGP in E-mail is bad@comma{} Mm'kay?}.

@noindent
Once @code{epa-mail-mode} is enabled, the following keys are assigned.
You can do it by @kbd{C-u 1 M-x epa-mail-mode} or through the Customize
interface.  Try @kbd{M-x customize-variable epa-global-mail-mode}.

@table @kbd
@item C-c C-e C-d and C-c C-e d
@kindex C-c C-e C-d
@kindex C-c C-e d
@findex epa-mail-decrypt
Decrypt OpenPGP armors in the current buffer.

@item C-c C-e C-v and C-c C-e v
@kindex C-c C-e C-v
@kindex C-c C-e v
@findex epa-mail-verify
Verify OpenPGP cleartext signed messages in the current buffer.

@item C-c C-e C-s and C-c C-e s
@kindex C-c C-e C-s
@kindex C-c C-e s
@findex epa-mail-sign
Compose a signed message from the current buffer, using your default
key.  With a prefix argument, select the key to use interactively.

@item C-c C-e C-e and C-c C-e e
@kindex C-c C-e C-e
@kindex C-c C-e e
@findex epa-mail-encrypt
@vindex epa-mail-aliases
Compose an encrypted message from the current buffer.
By default it tries to build the recipient list from @samp{to},
@samp{cc}, and @samp{bcc} fields of the mail header.  To include your
key in the recipient list, use @samp{encrypt-to} option in
@file{~/.gnupg/gpg.conf}.  This function translates recipient
addresses using the @code{epa-mail-aliases} list.  You can also
use that option to ignore specific recipients for encryption purposes.

With prefix argument, asks you to select the recipients interactively,
whether to sign, and which key(s) to sign with.
@end table

@node Encrypting/decrypting gpg files
@section Encrypting/decrypting gpg files
By default, every file whose name ends with @file{.gpg} will be
treated as encrypted.  That is, when you open such a file, the
decrypted text is inserted in the buffer rather than encrypted one.
Similarly, when you save the buffer to a @file{foo.gpg} file,
encrypted data is written.

When you save a buffer, say, to file @file{foo.gpg} for the first
time, EasyPG Assistant presents you a list of keys in a new buffer
@file{*Keys*} where you can select recipients for encryption.
@xref{Key management} for a description of the format of that buffer.
You can streamline this recipient selection step by customizing
variables @code{epa-file-encrypt-to} and @code{epa-file-select-keys},
see below.

If you do not select any recipient during this step, EasyPG Assistant
uses symmetric encryption.  As a consequence, you have to enter the
passphrase twice for every buffer save and every so often for file
reads, since the gpg-agent caches your passphrase for file reads at
least for some time, but not for buffer saves.

If you have created your own keypair@footnote{For encryption and
decryption of files you do not intend to share you do not have to use
an email address as recipient during creation of the keypair.  You can
also use some free-form string that gives information on the use of
the keypair, like @code{backup} or @code{account database}.} you can
select that as recipient, and EasyPG Assistant uses public key
encryption for that file.  Since encryption is performed with your
public key, no passphrase is prompted for the buffer save, but you
will be prompted for your passphrase for file reads every now and
then, depending on the gpg-agent cache configuration.

To encrypt and decrypt files as described above EasyPG Assistant under
certain circumstances uses intermediate tempory files that contain the
plain-text contents of the files to be encrypted or decrypted.  It
creates them below the directory returned by function
@code{temporary-file-directory}.  If you want to be sure not to leave
any plain-text traces, use an encrypted file systems at least for that
directory.

The file name pattern for encrypted files can be controlled by
@code{epa-file-name-regexp}.

@defvar epa-file-name-regexp
Regexp which matches filenames treated as encrypted.
@end defvar

You can disable this behavior with @kbd{M-x epa-file-disable}, and
then get it back with @kbd{M-x epa-file-enable}.

@deffn Command epa-file-disable
Disable automatic encryption/decryption of *.gpg files.
@end deffn

@deffn Command epa-file-enable
Enable automatic encryption/decryption of *.gpg files.
@end deffn

@noindent
By default, @code{epa-file} will try to use symmetric encryption, aka
password-based encryption.  If you want to use public key encryption
instead, do @kbd{M-x epa-file-select-keys}, which pops up the key
selection dialog.

@deffn Command epa-file-select-keys
Select recipient keys to encrypt the currently visiting file with
public key encryption.
@end deffn

You can also change the default behavior with the variable
@code{epa-file-select-keys}.

@defvar epa-file-select-keys
Control whether or not to pop up the key selection dialog.
@end defvar

For frequently visited files, it might be a good idea to tell Emacs
which encryption method should be used through @xref{File Variables, ,
, emacs, the Emacs Manual}.  Use the @code{epa-file-encrypt-to} local
variable for this.
@vindex epa-file-encrypt-to

For example, if you want an Elisp file to be encrypted with a
public key associated with an email address @samp{ueno@@unixuser.org},
add the following line to the beginning of the file.

@cartouche
@lisp
;; -*- epa-file-encrypt-to: ("ueno@@unixuser.org") -*-
@end lisp
@end cartouche

Instead, if you want the file always (regardless of the value of the
@code{epa-file-select-keys} variable) encrypted with symmetric
encryption, change the line as follows.

@cartouche
@lisp
;; -*- epa-file-encrypt-to: nil -*-
@end lisp
@end cartouche

Other variables which control the automatic encryption/decryption
behavior are below.

@defvar epa-file-cache-passphrase-for-symmetric-encryption
If non-@code{nil}, cache passphrase for symmetric encryption.  The
default value is @code{nil}.

For security reasons, this option is turned off by default and not
recommended to use.  Instead, consider using the gpg-agent, which in
many cases can do the same job, and does it in a safer way.
@xref{Caching Passphrases} for more information.
@end defvar

@defvar epa-file-inhibit-auto-save
If non-@code{nil}, disable auto-saving when opening an encrypted file.
The default value is @code{t}.
@end defvar

@node Querying a key server
@section Querying a key server

The @code{epa-search-keys} command can be used to query a
@acronym{GPG} key server.  Emacs will then pop up a buffer that lists
the matches, and you can then fetch (and add) keys to your personal
key ring.

In the key search buffer, you can use the @kbd{f} command to mark keys
for fetching, and then @kbd{x} to fetch the keys (and incorporate them
into your key ring).

The @code{epa-keyserver} variable says which server to query.


@node GnuPG version compatibility
@chapter GnuPG version compatibility

As of June 2023, there are three active branches of GnuPG: 2.4,
2.2, and 1.4.  All those branches should work flawlessly with Emacs
with basic use-cases.  They have, however, some incompatible
characteristics, which might be visible when used from Emacs.

@itemize
@item
The key store format used by GnuPG 2.1 is incompatible with 1.4.  That
means, a key created with GnuPG 2.1 is not visible with 1.4.

@item
GnuPG 2.1 uses a fixed address for the Unix domain socket used to
communicate with gpg-agent.  The @code{GPG_AGENT_INFO} environment
variable, which is used by GnuPG 2.0 and 1.4, is ignored.  That means,
if your system has both GnuPG 2.1 and 1.4, the gpg command from GnuPG
1.4 is not able to use gpg-agent provided by 2.1 (at least out of box).

@item
GnuPG 2.1 (2.1.5 or later) has a mechanism to direct the Pinentry
password prompt to the Emacs minibuffer@footnote{To enable this
feature, add @samp{allow-emacs-pinentry} to
@file{~/.gnupg/gpg-agent.conf} and let gpg-agent reload the
configuration, with: @samp{gpgconf --reload gpg-agent}}, which would
be useful when you use Emacs remotely or from a text-only terminal.
That feature is not available in other versions, and more
specifically, with 2.0 (as of 2.0.29), there is no way to avoid the
graphical prompt.
@end itemize


@node GnuPG Pinentry
@chapter GnuPG Pinentry

An important component of the GnuPG suite is the Pinentry, which
allows for secure entry of passphrases requests by GnuPG.  GnuPG
delivers various different programs as Pinentry, ranging from bland
TTY-only @samp{pinentry-tty} to fancy graphical dialogues for various
desktop environments, like @samp{pinentry-gnome3}.  Your operating
system usually determines which of these is used by default.

With some configuration Emacs can also play the role of a Pinentry.
There are three different scenarios possible@footnote{Not all
operating systems and distributions support all of the above
scenarios.  As of June 2023 Debian GNU/Linux, for example, supports
only the first of them due to security concerns.}:

@enumerate
@item Use Emacs only for GnuPG requests that are triggered by Emacs itself,
@item use Emacs for all GnuPG requests, or
@item use Emacs for all GnuPG requests with other Pinentry as fallback.
@end enumerate

FIXME: Brush the following paragraphs up.

1.: Ensure allow-loopback-pinentry is is configured for the GPG agent,
which should be the default.  Configure epg-pinentry-mode to
`loopback.

2.: Make pinentry-emacs the default pinentry by means of your
operating system.  Install package pinentry from GNU ELPA and execute
M-x pinentry-start to start the Pinentry service.  All GnuPG
passphrase requests should result in a minibuffer prompt in the
running Emacs.  If Emacs or pinentry service are not running,
passphrase requests fail.

3.: Ensure other Pinentry supports Emacs prompt.  pinentry-curses
does, for example.  Configure option allow-emacs-pinentry in
gpg-agent.conf.  Set environment variable INSIDE_EMACS for the calling
process.  Install package pinentry.  Now if Emacs is running and
pinentry-start has been exeucted, all GnuPG passphrase requests should
result in a minibuffer prompt in the running Emacs.  If Emacs or
Pinentry service are not running, GnuPG uses the regular Pinentry
instead.

First alternative can be configured in addition to onw of the others:
Requests triggered from within Emacs (like opening a gpg-encrypted
file) are handled through loopback pinentry, Requests outside of emacs
through pinentry feature.

Note that the selection of a concrete Pinentry program determines only
@emph{how} GnuPG queries for passphrases and not @emph{how often}.
For the latter question @xref{Caching Passphrases}.

@node Caching Passphrases
@chapter Caching Passphrases

Typing passphrases is a troublesome task if you frequently open and
close the same file.  GnuPG and EasyPG Assistant provide mechanisms to
remember your passphrases for a limited time.  Using these, you only
need to re-enter the passphrase occasionally.  However, the
configuration is a bit confusing since it depends on your GnuPG
installation @xref{GnuPG version compatibility}, encryption method
(symmetric or public key), and whether or not you want to use
gpg-agent (which is mandatory for GnuPG 2.0 and later).  Here are some
questions:

@enumerate
@item Do you use GnuPG version 2.1 or 2.0 instead of GnuPG version 1.4?
@item Do you use symmetric encryption rather than public key encryption?
@item Do you want to use gpg-agent?
@end enumerate

Here are configurations depending on your answers:

@multitable {111} {222} {333} {configuration configuration configuration}
@item @b{1} @tab @b{2} @tab @b{3} @tab Configuration
@item Yes @tab Yes @tab Yes @tab Set up gpg-agent.
@item Yes @tab Yes @tab No @tab You can't, without gpg-agent.
@item Yes @tab No @tab Yes @tab Set up gpg-agent.
@item Yes @tab No @tab No @tab You can't, without gpg-agent.
@item No @tab Yes @tab Yes @tab Set up elisp passphrase cache.
@item No @tab Yes @tab No @tab Set up elisp passphrase cache.
@item No @tab No @tab Yes @tab Set up gpg-agent.
@item No @tab No @tab No @tab You can't, without gpg-agent.
@end multitable

To set up gpg-agent, follow the instruction in GnuPG manual.
@pxref{Invoking GPG-AGENT, , Invoking GPG-AGENT, gnupg}.

To set up elisp passphrase cache, set
@code{epa-file-cache-passphrase-for-symmetric-encryption}.
@xref{Encrypting/decrypting gpg files}.

@node Bug Reports
@chapter Bug Reports

Bugs and problems with EasyPG Assistant are actively worked on by the
Emacs development team.  Feature requests and suggestions are also
more than welcome.  Use @kbd{M-x report-emacs-bug}, @pxref{Bugs, ,
Bugs, emacs, Reporting Bugs}.

When submitting a bug report, please try to describe in excruciating
detail the steps required to reproduce the problem.  Also try to
collect necessary information to fix the bug, such as:

@itemize @bullet
@item the GnuPG version.  Send the output of @samp{gpg --version}.
@item the GnuPG configuration.  Send the contents of @file{~/.gnupg/gpg.conf}.
@end itemize

Before reporting the bug, you should set @code{epg-debug} in the
@file{~/.emacs} file and repeat the bug.  Then, include the contents
of the @file{ *epg-debug*} buffer.  Note that the first letter of the
buffer name is a whitespace.

@node GNU Free Documentation License
@appendix GNU Free Documentation License
@include doclicense.texi

@node Key Index
@unnumbered Key Index
@printindex ky

@node Function Index
@unnumbered Function Index
@printindex fn

@node Variable Index
@unnumbered Variable Index
@printindex vr

@bye

@c End: