EasyPG Assistant user's manual

EasyPG Assistant is an Emacs user interface to GNU Privacy Guard (GnuPG, see Top).

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.

This file describes EasyPG Assistant 1.0.0.

Copyright © 2007–2013 Free Software Foundation, Inc.

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.”

Overview
Quick start
Commands
Caching Passphrases
Bug Reports
GNU Free Documentation License The license for this documentation.

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1 Overview

EasyPG Assistant provides the following features.

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2 Quick start

EasyPG Assistant commands are prefixed by ‘epa-’. For example,

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

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3 Commands

This chapter introduces various commands for typical use cases.

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3.1 Key management

Probably the first step of using EasyPG Assistant is to browse your keyring. M-x epa-list-keys is corresponding to ‘gpg --list-keys’ from the command line.

— Command: epa-list-keys name mode

Show all keys matched with name from the public keyring.

The output looks as follows.

       u A5B6B2D4B15813FE Daiki Ueno <ueno@unixuser.org>

A character on the leftmost column indicates the trust level of the key. If it is ‘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 <TAB>. If you type <RET> or click button1 on an entry, you will see more detailed information about the key you selected.

      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

To browse your private keyring, use M-x epa-list-secret-keys.

— Command: epa-list-secret-keys name

Show all keys matched with name from the private keyring.

In ‘*Keys*’ buffer, several commands are available. The common use case is to export some keys to a file. To do that, type m to select keys, type 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.

— Command: epa-insert-keys keys

Insert selected keys after the point. It will let you select keys before insertion. By default, it will encode keys in the OpenPGP armor format.

— Command: epa-import-keys file

Import keys from file to your keyring.

— Command: epa-import-keys-region start end

Import keys from the current region between start and end to your keyring.

— Command: epa-import-armor-in-region start end

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

— Command: epa-delete-keys allow-secret

Delete selected keys. If allow-secret is non-nil, it also delete the secret keys.

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3.2 Cryptographic operations on regions

— Command: epa-decrypt-region start end

Decrypt the current region between start and end. It replaces the region with the decrypted text.

— Command: epa-decrypt-armor-in-region start end

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

— Command: epa-verify-region start end

Verify the current region between start and end. It sends the verification result to the minibuffer or a popup window. It replaces the region with the signed text.

— Command: epa-verify-cleartext-in-region

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

— Command: epa-sign-region start end signers type

Sign the current region between start and 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.

— Command: epa-encrypt-region start end recipients sign signers

Encrypt the current region between start and 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.

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3.3 Cryptographic operations on files

— Command: epa-decrypt-file file

Decrypt file.

— Command: epa-verify-file file

Verify file.

— Command: epa-sign-file file signers type

Sign file. If a prefix argument is given, it will let you select signing keys, and then a signature type.

— Command: epa-encrypt-file file recipients

Encrypt file. It will let you select recipients.

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3.4 Dired integration

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

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

The following keys are assigned.

: d
Decrypt marked files.
: v
Verify marked files.
: s
Sign marked files.
: e
Encrypt marked files.

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3.5 Mail-mode integration

EasyPG Assistant provides a minor mode 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 Inline OpenPGP in E-mail is bad, Mm'kay?.

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

C-c C-e C-d and C-c C-e d
Decrypt OpenPGP armors in the current buffer.
C-c C-e C-v and C-c C-e v
Verify OpenPGP cleartext signed messages in the current buffer.
C-c C-e C-s and C-c C-e s
Compose a signed message from the current buffer.
C-c C-e C-e and C-c C-e e
Compose an encrypted message from the current buffer. By default it tries to build the recipient list from ‘to’, ‘cc’, and ‘bcc’ fields of the mail header. To include your key in the recipient list, use ‘encrypt-to’ option in ~/.gnupg/gpg.conf.

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3.6 Encrypting/decrypting *.gpg files

By default, every file whose name ends with ‘.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 ‘foo.gpg’ file, encrypted data is written.

The file name pattern for encrypted files can be controlled by epa-file-name-regexp.

— Variable: epa-file-name-regexp

Regexp which matches filenames treated as encrypted.

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

— Command: epa-file-disable

Disable automatic encryption/decryption of *.gpg files.

— Command: epa-file-enable

Enable automatic encryption/decryption of *.gpg files.

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

— Command: epa-file-select-keys

Select recipient keys to encrypt the currently visiting file with public key encryption.

You can also change the default behavior with the variable epa-file-select-keys.

— Variable: epa-file-select-keys

Control whether or not to pop up the key selection dialog.

For frequently visited files, it might be a good idea to tell Emacs which encryption method should be used through See File Variables. Use the epa-file-encrypt-to local variable for this. For example, if you want an Elisp file should be encrypted with a public key associated with an email address ‘ueno@unixuser.org’, add the following line to the beginning of the file.

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

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

     ;; -*- epa-file-encrypt-to: nil -*-

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

— Variable: epa-file-cache-passphrase-for-symmetric-encryption

If non-nil, cache passphrase for symmetric encryption. The default value is nil.

— Variable: epa-file-inhibit-auto-save

If non-nil, disable auto-saving when opening an encrypted file. The default value is t.

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4 Caching Passphrases

Typing passphrases is an irritating task if you frequently open and close the same file. GnuPG and EasyPG Assistant provide mechanisms to remember your passphrases. However, the configuration is a bit confusing since it depends on your GnuPG installation (GnuPG version 1 or GnuPG version 2), encryption method (symmetric or public key), and whether or not you want to use gpg-agent. Here are some questions:

  1. Do you use GnuPG version 2 instead of GnuPG version 1?
  2. Do you use symmetric encryption rather than public key encryption?
  3. Do you want to use gpg-agent?

Here are configurations depending on your answers:

1 2 3 Configuration
Yes Yes Yes Set up gpg-agent.
Yes Yes No You can't, without gpg-agent.
Yes No Yes Set up gpg-agent.
Yes No No You can't, without gpg-agent.
No Yes Yes Set up elisp passphrase cache.
No Yes No Set up elisp passphrase cache.
No No Yes Set up gpg-agent.
No No No You can't, without gpg-agent.

To set up gpg-agent, follow the instruction in GnuPG manual. see Invoking GPG-AGENT.

To set up elisp passphrase cache, set epa-file-cache-passphrase-for-symmetric-encryption. See Encrypting/decrypting *.gpg files.

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5 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 M-x report-emacs-bug, see 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:

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

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Appendix A GNU Free Documentation License

Version 1.3, 3 November 2008
     Copyright © 2000, 2001, 2002, 2007, 2008, 2009 Free Software Foundation, Inc.
     http://fsf.org/
     
     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.
  1. PREAMBLE

    The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

    This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

  2. APPLICABILITY AND DEFINITIONS

    This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

    A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

    A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

    The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

    The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

    A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

    Examples of suitable formats for Transparent copies include plain ascii without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

    The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

    The “publisher” means any person or entity that distributes copies of the Document to the public.

    A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.

    The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

  3. VERBATIM COPYING

    You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

    You may also lend copies, under the same conditions stated above, and you may publicly display copies.

  4. COPYING IN QUANTITY

    If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

    If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

    If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

    It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

  5. MODIFICATIONS

    You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

    1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
    2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
    3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
    4. Preserve all the copyright notices of the Document.
    5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
    6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
    7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
    8. Include an unaltered copy of this License.
    9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
    10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
    11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
    12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
    13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
    14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
    15. Preserve any Warranty Disclaimers.

    If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

    You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

    You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

    The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

  6. COMBINING DOCUMENTS

    You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

    The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

    In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”

  7. COLLECTIONS OF DOCUMENTS

    You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

    You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

  8. AGGREGATION WITH INDEPENDENT WORKS

    A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

    If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

  9. TRANSLATION

    Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

    If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

  10. TERMINATION

    You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

    However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

    Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

    Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.

  11. FUTURE REVISIONS OF THIS LICENSE

    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Document.

  12. RELICENSING

    “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.

    “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

    “Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.

    An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

    The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

       Copyright (C)  year  your name.
       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, no Front-Cover Texts, and no Back-Cover
       Texts.  A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.” line with this:

         with the Invariant Sections being list their titles, with
         the Front-Cover Texts being list, and with the Back-Cover Texts
         being list.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.