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Versions: 00

dispatch                                                      J. Yasskin
Internet-Draft                                                    Google
Intended status: Informational                           August 30, 2017
Expires: March 3, 2018


              Use Cases and Requirements for Web Packages
                 draft-yasskin-webpackage-use-cases-00

Abstract

   This document lists use cases for signing and/or bundling collections
   of web pages, and extracts a set of requirements from them.

Note to Readers

   Discussion of this draft takes place on the ART area mailing list
   (art@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/search/?email_list=art.

   The source code and issues list for this draft can be found in
   https://github.com/WICG/webpackage.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 3, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Use cases . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Essential . . . . . . . . . . . . . . . . . . . . . . . .   3
       2.1.1.  Offline installation  . . . . . . . . . . . . . . . .   3
       2.1.2.  Offline browsing  . . . . . . . . . . . . . . . . . .   5
       2.1.3.  Save and share a web page . . . . . . . . . . . . . .   5
     2.2.  Nice-to-have  . . . . . . . . . . . . . . . . . . . . . .   6
       2.2.1.  Packaged Web Publications . . . . . . . . . . . . . .   6
       2.2.2.  Third-party security review . . . . . . . . . . . . .   7
       2.2.3.  Building packages from multiple libraries . . . . . .   7
       2.2.4.  CDNs  . . . . . . . . . . . . . . . . . . . . . . . .   8
       2.2.5.  Installation from a self-extracting executable  . . .   8
       2.2.6.  Ergonomic replacement for HTTP/2 PUSH . . . . . . . .   9
       2.2.7.  Packages in version control . . . . . . . . . . . . .   9
   3.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   9
     3.1.  Essential . . . . . . . . . . . . . . . . . . . . . . . .  10
       3.1.1.  Indexed by URL  . . . . . . . . . . . . . . . . . . .  10
       3.1.2.  Request headers . . . . . . . . . . . . . . . . . . .  10
       3.1.3.  Response headers  . . . . . . . . . . . . . . . . . .  10
       3.1.4.  Signing as an origin  . . . . . . . . . . . . . . . .  10
       3.1.5.  Random access . . . . . . . . . . . . . . . . . . . .  11
       3.1.6.  Resources from multiple origins in a package  . . . .  11
       3.1.7.  Cryptographic agility . . . . . . . . . . . . . . . .  11
       3.1.8.  Unsigned content  . . . . . . . . . . . . . . . . . .  11
       3.1.9.  Certificate revocation  . . . . . . . . . . . . . . .  11
       3.1.10. Downgrade prevention  . . . . . . . . . . . . . . . .  11
       3.1.11. Metadata  . . . . . . . . . . . . . . . . . . . . . .  11
       3.1.12. Implementations are hard to get wrong . . . . . . . .  12
     3.2.  Nice to have  . . . . . . . . . . . . . . . . . . . . . .  12
       3.2.1.  Streamed loading  . . . . . . . . . . . . . . . . . .  12
       3.2.2.  Cross-signatures  . . . . . . . . . . . . . . . . . .  12
       3.2.3.  Binary  . . . . . . . . . . . . . . . . . . . . . . .  12
       3.2.4.  Deduplication of diamond dependencies . . . . . . . .  12
       3.2.5.  Old crypto can be removed . . . . . . . . . . . . . .  12
       3.2.6.  Compress transfers  . . . . . . . . . . . . . . . . .  13
       3.2.7.  Compress stored packages  . . . . . . . . . . . . . .  13
       3.2.8.  Subsetting and reordering . . . . . . . . . . . . . .  13
       3.2.9.  Packaged validity information . . . . . . . . . . . .  13
       3.2.10. Signing uses existing TLS certificates  . . . . . . .  13



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       3.2.11. External dependencies . . . . . . . . . . . . . . . .  13
       3.2.12. Trailing length . . . . . . . . . . . . . . . . . . .  13
   4.  Non-goals . . . . . . . . . . . . . . . . . . . . . . . . . .  13
     4.1.  Store confidential data . . . . . . . . . . . . . . . . .  14
     4.2.  Generate packages on the fly  . . . . . . . . . . . . . .  14
     4.3.  Non-origin identity . . . . . . . . . . . . . . . . . . .  14
     4.4.  DRM . . . . . . . . . . . . . . . . . . . . . . . . . . .  14
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     7.1.  Informative References  . . . . . . . . . . . . . . . . .  15
     7.2.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .  16
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  17
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   People would like to use content offline and in other situations
   where there isn't a direct connection to the server where the content
   originates.  However, it's difficult to distribute and verify the
   authenticity of applications and content without a connection to the
   network.  The W3C has addressed running applications offline with
   Service Workers ([ServiceWorkers]), but not the problem of
   distribution.

   Previous attempts at packaging web resources (e.g.  Resource Packages
   [3] and the W3C TAG's packaging proposal [4]) were motivated by
   speeding up the download of resources from a single server, which is
   probably better achieved through other mechanisms like HTTP/2 PUSH,
   possibly augmented with a simple manifest of URLs a page plans to use
   [5].  This attempt is instead motivated by avoiding a connection to
   the origin server at all.  It may still be useful for the earlier use
   cases, so they're still listed, but they're not primary.

2.  Use cases

   These use cases are in rough descending priority order.  If use cases
   have conflicting requirements, the design should enable more
   important use cases.

2.1.  Essential

2.1.1.  Offline installation

   Alex can download a file containing a website (a PWA [6]) including a
   Service Worker from origin "O", and transmit it to their peer Bailey,
   and then Bailey can install the Service Worker with a proof that it




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   came from "O".  This saves Bailey the bandwidth costs of transferring
   the website.

   Associated requirements:

   o  Indexed by URL: Resources on the web are addressed by URL.

   o  Request headers: If Bailey's running a different browser from Alex
      or has a different language configured, the "accept*" headers are
      important for selecting which resource to use at each URL.

   o  Response headers: The meaning of a resource is heavily influenced
      by its HTTP response headers.

   o  Signing as an origin: To prove that the file came from "O".

   o  Signing uses existing TLS certificates: So "O" doesn't have to
      spend lots of money buying a specialized certificate.

   o  Resources from multiple origins in a package: So the site can be
      built from multiple components (Section 2.2.3).

   o  Cryptographic agility: Today's algorithms will eventually be
      obsolete and will need to be replaced.

   o  Certificate revocation: "O"'s certificate might be compromised or
      mis-issued, and the attacker shouldn't then get an infinite
      ability to mint packages.

   o  Downgrade prevention: "O"'s site might have an XSS vulnerability,
      and attackers with an old signed package shouldn't be able to take
      advantage of the XSS forever.

   o  Metadata: The browser needs to know which resource within a
      package file to treat as its Service Worker and/or initial HTML
      page.

2.1.1.1.  Online use

   Bailey may have an internet connection through which they can, in
   real time, fetch updates to the package they received from Alex.

2.1.1.2.  Fully offline use

   Or Bailey may not have any internet connection a significant fraction
   of the time, either because they have no internet at all, because
   they turn off internet except when intentionally downloading content,
   or because they use up their plan partway through each month.



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   Associated requirements beyond Offline installation:

   o  Packaged validity information: Even without a direct internet
      connection, Bailey should be able to check that their package is
      still valid.

2.1.2.  Offline browsing

   Alex can download a file containing a large website (e.g.  Wikipedia)
   from its origin, save it to transferrable storage (e.g. an SD card),
   and hand it to their peer Bailey.  Then Bailey can browse the website
   with a proof that it came from "O".  Bailey may not have the storage
   space to copy the website before browsing it.

   Associated requirements beyond Offline installation:

   o  Random access: To avoid needing a long linear scan before using
      the content.

   o  Compress stored packages: So that more content can fit on the same
      storage device.

2.1.3.  Save and share a web page

   Casey is viewing a web page and wants to save it either for offline
   use or to show it to their friend Dakota.  Since Casey isn't the web
   page's author, they don't have the private key needed to sign the
   page.  Browsers currently allow their users to save pages, but each
   browser uses a different format (MHTML, Web Archive, or files in a
   directory), so Dakota and Casey would need to be using the same
   browser.  Casey could also take a screenshot, at the cost of losing
   links and accessibility.

   Associated requirements:

   o  Unsigned content: A client can't sign content as another origin.

   o  Resources from multiple origins in a package: General web pages
      include resources from multiple origins.

   o  Indexed by URL: Resources on the web are addressed by URL.

   o  Response headers: The meaning of a resource is heavily influenced
      by its HTTP response headers.







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2.2.  Nice-to-have

2.2.1.  Packaged Web Publications

   The W3C's Publishing Working Group [7], merged from the International
   Digital Publishing Forum (IDPF) and in charge of EPUB maintenance,
   wants to be able to create publications on the web and then let them
   be copied to different servers or to other users via arbitrary
   protocols.  See their Packaged Web Publications use cases [8] for
   more details.

   Associated requirements:

   o  Indexed by URL: Resources on the web are addressed by URL.

   o  Signing as an origin: So that readers can be sure their copy is
      authentic and so that copying the package preserves the URLs of
      the content inside it.

   o  Downgrade prevention: An early version of a publication might
      contain incorrect content, and a publisher should be able to
      update that without worrying that an attacker can still show the
      old content to users.

   o  Metadata: A publication can have copyright and licensing concerns;
      a title, author, and cover image; an ISBN or DOI name; etc.; which
      should be included when that publication is packaged.

   Other requirements are similar to those from Offline installation:

   o  Random access: To avoid needing a long linear scan before using
      the content.

   o  Compress stored packages: So that more content can fit on the same
      storage device.

   o  Request headers: If different users' browsers have different
      capabilities or preferences, the "accept*" headers are important
      for selecting which resource to use at each URL.

   o  Response headers: The meaning of a resource is heavily influenced
      by its HTTP response headers.

   o  Signing uses existing TLS certificates: So a publisher doesn't
      have to spend lots of money buying a specialized certificate.

   o  Cryptographic agility: Today's algorithms will eventually be
      obsolete and will need to be replaced.



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   o  Certificate revocation: The publisher's certificate might be
      compromised or mis-issued, and an attacker shouldn't then get an
      infinite ability to mint packages.

2.2.2.  Third-party security review

   Some users may want to grant certain permissions only to applications
   that have been reviewed for security by a trusted third party.  These
   third parties could provide guarantees similar to those provided by
   the iOS, Android, or ChromeOS app stores, which might allow browsers
   to offer more powerful capabilities than have been deemed safe for
   unaudited websites.

   Binary transparency for websites is similar: like with Certificate
   Transparency [RFC6962], the transparency logs would sign the content
   of the package to provide assurance that experts had a chance to
   audit the exact package a client received.

   Associated requirements:

   o  Cross-signatures

2.2.3.  Building packages from multiple libraries

   Large programs are built from smaller components.  In the case of the
   web, components can be included either as Javascript files or as
   "<iframe>"d subresources.  In the first case, the packager could copy
   the JS files to their own origin; but in the second, it may be
   important for the "<iframe>"d resources to be able to make same-
   origin [9] requests back to their own origin, for example to
   implement federated sign-in.

   Associated requirements:

   o  Resources from multiple origins in a package: Each component may
      come from its own origin.

   o  Deduplication of diamond dependencies: If we have dependencies
      A->B->D and A->C->D, it's important that a request for a D
      resource resolves to a single resource that both B and C can
      handle.

2.2.3.1.  Shared libraries

   In ecosystems like Electron [10] and Node [11], many packages may
   share some common dependencies.  The cost of downloading each package
   can be greatly reduced if the package can merely point at other
   dependencies to download instead of including them all inline.



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   Associated requirements:

   o  External dependencies

2.2.4.  CDNs

   CDNs want to re-publish other origins' content so readers can access
   it more quickly or more privately.  Currently, to attribute that
   content to the original origin, they need the full ability to publish
   arbitrary content under that origin's name.  There should be a way to
   let them attribute only the exact content that the original origin
   published.

   Web Packages would allow CDNs to publish content as another site as
   long as the user visited a URL explicitly mentioning the CDN.

   CDNs want to serve only the bytes that most optimally represent the
   content the current user needs, even though the origin needs to
   provide representations for all users.  Think PNG vs WebP and small
   vs large resolutions.

   Associated requirements:

   o  Streamed loading: To get optimal performance, the browser should
      be able to start loading early resources before the CDN finishes
      sending the whole package.

   o  Signing as an origin: To prove the content came from the original
      origin.

   o  Subsetting and reordering: If a package includes both WebP and PNG
      versions of an image, the CDN should be able to select the best
      one to send to each client.

   o  Compress transfers

2.2.5.  Installation from a self-extracting executable

   The Node and Electron communities would like to install packages
   using self-extracting executables.  The traditional way to design a
   self-extracting executable is to concatenate the package to the end
   of the executable, have the executable look for a length at its own
   end, and seek backwards from there for the start of the package.

   Associated requirements:

   o  Trailing length




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2.2.6.  Ergonomic replacement for HTTP/2 PUSH

   HTTP/2 PUSH ([RFC7540], section 8.2) is hard for developers to
   configure, and an explicit package format might be easier.

   Trying to bundle resources in order to speed up page loads has a long
   history, including Resource Packages [12] from 2010 and the W3C TAG's
   packaging proposal [13] from 2015.

   However, the HTTPWG is doing a lot of work to let servers optimize
   the PUSHed data, and packaging would either have to re-do that or
   accept lower performance.  Accepting lower performance might be
   worthwhile if it allows more developers to adopt the smaller
   optimization.

   Associated requirements:

   o  Streamed loading: If the whole package has to be downloaded before
      the browser can load a piece, this will definitely be slower than
      PUSH.

   o  Compress transfers: I believe PUSHed resources cannot keep a
      single compression state across resource boundaries, so this might
      be an advantage for packaging.

   o  Indexed by URL: Resources on the web are addressed by URL.

   o  Request headers: PUSH_PROMISE [14] ([RFC7540], section 6.6)
      includes request headers.

   o  Response headers: PUSHed resources include their response headers.

2.2.7.  Packages in version control

   Once packages are generated, they should be stored in version
   control.  Many popular VC systems auto-detect text files in order to
   "fix" their line endings.  If the first bytes of a package look like
   text, while later bytes store binary data, VC may break the package.

   Associated requirements:

   o  Binary

3.  Requirements







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3.1.  Essential

3.1.1.  Indexed by URL

   Resources should be keyed by URLs, matching how browsers look
   resources up over HTTP.

3.1.2.  Request headers

   Resource keys should include request headers like "accept" and
   "accept-language", which allows content-negotiated resources to be
   represented.

   This would require an extension to [MHTML], which uses the "content-
   location" response header to encode the requested URL, but has no way
   to encode other request headers.  MHTML also has no instructions for
   handling multiple resources with the same "content-location".

   This also requires an extension to [ZIP]: we'd need to encode the
   request headers into ZIP's filename fields.

3.1.3.  Response headers

   Resources should include their HTTP response headers, like "content-
   type", "content-encoding", "expires", "content-security-policy", etc.

   This requires an extension to [ZIP]: we'd need something like [JAR]'s
   "META-INF" directory to hold extra metadata beyond the resource's
   body.

3.1.4.  Signing as an origin

   Resources within a package are provably from an entity with the
   ability to serve HTTPS requests for those resources' origin
   [RFC6454].

   Resources within a package are provably from an entity with the
   ability to serve HTTPS requests for those resources' origin
   [RFC6454].

   Note that previous attempts to sign HTTP messages
   ([I-D.thomson-http-content-signature], [I-D.burke-content-signature],
   and [I-D.cavage-http-signatures]) omit a description of how a client
   should use a signature to prove that a resource comes from a
   particular origin, and they're probably not usable for that purpose.

   This would require an extension to the [ZIP] format, similar to
   [JAR]'s signatures.



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   In any cryptographic system, the specification is responsible to make
   correct implementations easier to deploy than incorrect
   implementations (Section 3.1.12).

3.1.5.  Random access

   When a package is stored on disk, the browser can access arbitrary
   resources without a linear scan.

   [MHTML] would need to be extended with an index of the byte offsets
   of each contained resource.

3.1.6.  Resources from multiple origins in a package

   A package from origin "A" can contain resources from origin "B"
   authenticated at the same level as those from "A".

3.1.7.  Cryptographic agility

   Obsolete cryptographic algorithms can be replaced.

   Planning to upgrade the cryptography also means we should include
   some way to know when it's safe to remove old cryptography
   (Section 3.2.5).

3.1.8.  Unsigned content

   Alex can create their own package without a CA-signed certificate,
   and Bailey can view the content of the package.

3.1.9.  Certificate revocation

   When a package is signed by a revoked certificate, online browsers
   can detect this reasonably quickly.

3.1.10.  Downgrade prevention

   Attackers can't cause a browser to trust an older, vulnerable version
   of a package after the browser has seen a newer version.

3.1.11.  Metadata

   Metadata like that found in the W3C's Application Manifest
   [W3C.WD-appmanifest-20170828] can help a client know how to load and
   display a package.






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3.1.12.  Implementations are hard to get wrong

   The design should incorporate aspects that tend to cause incorrect
   implementations to get noticed quickly, and avoid aspects that are
   easy to implement incorrectly.  For example:

   o  Explicitly specifying a cryptographic algorithm identifier in
      [RFC7515] made it easy for implementations to trust that
      algorithm, which caused vulnerabilities [15].

   o  [ZIP]'s duplicate specification of filenames makes it easy for
      implementations to check the signature of one copy but use the
      other [16].

   o  Following Langley's Law [17] when possible makes it hard to deploy
      incorrect implementations.

3.2.  Nice to have

3.2.1.  Streamed loading

   The browser can load a package as it downloads.

   This conflicts with ZIP, since ZIP's index is at the end.

3.2.2.  Cross-signatures

   Third-parties can vouch for packages by signing them.

3.2.3.  Binary

   The format is identified as binary by tools that might try to "fix"
   line endings.

   This conflicts with using an [MHTML]-based format.

3.2.4.  Deduplication of diamond dependencies

   Nested packages that have multiple dependency routes to the same sub-
   package, can be transmitted and stored with only one copy of that
   sub-package.

3.2.5.  Old crypto can be removed

   The ecosystem can identify when an obsolete cryptographic algorithm
   is no longer needed and can be removed.





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3.2.6.  Compress transfers

   Transferring a package over the network takes as few bytes as
   possible.  This is an easier problem than Compress stored packages
   since it doesn't have to preserve Random access.

3.2.7.  Compress stored packages

   Storing a package on disk takes as few bytes as possible.

3.2.8.  Subsetting and reordering

   Resources can be removed from and reordered within a package, without
   breaking signatures (Section 3.1.4).

3.2.9.  Packaged validity information

   Certificate revocation and Downgrade prevention information can
   itself be packaged or included in other packages.

3.2.10.  Signing uses existing TLS certificates

   A "normal" TLS certificate can be used for signing packages.
   Avoiding extra requirements like "code signing" certificates makes
   packaging more accessible to all sites.

3.2.11.  External dependencies

   Sub-packages can be "external" to the main package, meaning the
   browser will need to either fetch them separately or already have
   them.  (#35, App Installer Story [18])

3.2.12.  Trailing length

   The package's length in bytes appears a fixed offset from the end of
   the package.

   This conflicts with [MHTML].

4.  Non-goals

   Some features often come along with packaging and signing, and it's
   important to explicitly note that they don't appear in the list of
   Requirements.







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4.1.  Store confidential data

   Packages are designed to hold public information and to be shared to
   people with whom the original author never has an interactive
   connection.  In that situation, there's no way to keep the contents
   confidential: even if they were encrypted, to make the data public,
   anyone would have to be able to get the decryption key.

   It's possible to maintain something similar to confidentiality for
   non-public packaged data, but doing so complicates the format design
   and can give users a false sense of security.

   We believe we'll cause fewer privacy breaches if we omit any
   mechanism for encrypting data, than if we include something and try
   to teach people when it's unsafe to use.

4.2.  Generate packages on the fly

   See discussion at WICG/webpackage#6 [19].

4.3.  Non-origin identity

   A package can be primarily identified as coming from something other
   than a Web Origin [20].

4.4.  DRM

   Special support for blocking access to downloaded content based on
   licensing.  Note that DRM systems can be shipped inside the package
   even if the packaging format doesn't specifically support them.

5.  Security Considerations

   The security considerations will depend on the solution designed to
   satisfy the above requirements.  See
   [I-D.yasskin-dispatch-web-packaging] for one possible set of security
   considerations.

6.  IANA Considerations

   This document has no actions for IANA.

7.  References








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7.1.  Informative References

   [I-D.burke-content-signature]
              Burke, B., "HTTP Header for digital signatures", draft-
              burke-content-signature-00 (work in progress), March 2011.

   [I-D.cavage-http-signatures]
              Cavage, M. and M. Sporny, "Signing HTTP Messages", draft-
              cavage-http-signatures-07 (work in progress), July 2017.

   [I-D.thomson-http-content-signature]
              Thomson, M., "Content-Signature Header Field for HTTP",
              draft-thomson-http-content-signature-00 (work in
              progress), July 2015.

   [I-D.yasskin-dispatch-web-packaging]
              Yasskin, J., "Web Packaging", draft-yasskin-dispatch-web-
              packaging-00 (work in progress), June 2017.

   [JAR]      "JAR File Specification", 2014,
              <https://docs.oracle.com/javase/7/docs/technotes/guides/
              jar/jar.html>.

   [MHTML]    Palme, J., Hopmann, A., and N. Shelness, "MIME
              Encapsulation of Aggregate Documents, such as HTML
              (MHTML)", RFC 2557, DOI 10.17487/RFC2557, March 1999,
              <https://www.rfc-editor.org/info/rfc2557>.

   [RFC6454]  Barth, A., "The Web Origin Concept", RFC 6454,
              DOI 10.17487/RFC6454, December 2011, <https://www.rfc-
              editor.org/info/rfc6454>.

   [RFC6962]  Laurie, B., Langley, A., and E. Kasper, "Certificate
              Transparency", RFC 6962, DOI 10.17487/RFC6962, June 2013,
              <https://www.rfc-editor.org/info/rfc6962>.

   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <https://www.rfc-editor.org/info/rfc7515>.

   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015, <https://www.rfc-
              editor.org/info/rfc7540>.







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   [ServiceWorkers]
              Russell, A., Song, J., Archibald, J., and M.
              Kruisselbrink, "Service Workers 1", World Wide Web
              Consortium WD WD-service-workers-1-20161011, October 2016,
              <https://www.w3.org/TR/2016/WD-service-workers-
              1-20161011>.

   [W3C.WD-appmanifest-20170828]
              Caceres, M., Christiansen, K., Lamouri, M., Kostiainen,
              A., and R. Dolin, "Web App Manifest", World Wide Web
              Consortium WD WD-appmanifest-20170828, August 2017,
              <https://www.w3.org/TR/2017/WD-appmanifest-20170828>.

   [ZIP]      "APPNOTE.TXT - .ZIP File Format Specification", October
              2014, <https://pkware.cachefly.net/webdocs/casestudies/
              APPNOTE.TXT>.

7.2.  URIs

   [1] https://www.mnot.net/blog/2010/02/18/resource_packages

   [2] https://w3ctag.github.io/packaging-on-the-web/

   [3] https://lists.w3.org/Archives/Public/public-web-
       perf/2015Jan/0038.html

   [4] https://developers.google.com/web/progressive-web-apps/checklist

   [5] https://www.w3.org/publishing/groups/publ-wg/

   [6] https://www.w3.org/TR/pwp-ucr/#pwp

   [7] https://html.spec.whatwg.org/multipage/origin.html#same-origin

   [8] https://electron.atom.io/

   [9] https://nodejs.org/en/

   [10] https://www.mnot.net/blog/2010/02/18/resource_packages

   [11] https://w3ctag.github.io/packaging-on-the-web/

   [12] http://httpwg.org/specs/rfc7540.html#PUSH_PROMISE

   [13] https://paragonie.com/blog/2017/03/jwt-json-web-tokens-is-bad-
        standard-that-everyone-should-avoid





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   [14] https://nakedsecurity.sophos.com/2013/07/10/anatomy-of-a-
        security-hole-googles-android-master-key-debacle-explained/

   [15] https://blog.gerv.net/2016/09/introducing-deliberate-protocol-
        errors-langleys-law/

   [16] https://github.com/WICG/webpackage/issues/35

   [17] https://github.com/WICG/webpackage/
        issues/6#issuecomment-275746125

   [18] https://html.spec.whatwg.org/multipage/browsers.html#concept-
        origin

Appendix A.  Acknowledgements

Author's Address

   Jeffrey Yasskin
   Google

   Email: jyasskin@chromium.org





























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