Cryptographic Hyperlinks
draft-sporny-hashlink-04

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Network Working Group                                          M. Sporny
Internet-Draft                                            Digital Bazaar
Intended status: Standards Track                            Nov 18, 2019
Expires: May 21, 2020

                        Cryptographic Hyperlinks
                        draft-sporny-hashlink-04

Abstract

   When using a hyperlink to fetch a resource from the Internet, it is
   often useful to know if the resource has changed since the data was
   published.  Cryptographic hashes, such as SHA-256, are often used to
   determine if published data has changed in unexpected ways.  Due to
   the nature of most hyperlinks, the cryptographic hash is often
   published separately from the link itself.  This specification
   describes a data model and serialization formats for expressing
   cryptographically protected hyperlinks.  The mechanisms described in
   the document enables a system to publish a hyperlink in a way that
   empowers a consuming application to determine if the resource
   associated with the hyperlink has changed in unexpected ways.

Feedback

   This specification is a work product of the W3C Digital Verification
   Community Group [1] and the W3C Credentials Community Group [2].
   Feedback related to this specification should be logged in the issue
   tracker [3] or be sent to public-credentials@w3.org [4].

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

   This Internet-Draft will expire on May 21, 2020.

Sporny                    Expires May 21, 2020                  [Page 1]
Internet-Draft          Cryptographic Hyperlinks                Nov 2019

Copyright Notice

   Copyright (c) 2019 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Multiple Encodings  . . . . . . . . . . . . . . . . . . .   4
   2.  Hashlink Data Model . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  The Resource Hash . . . . . . . . . . . . . . . . . . . .   4
     2.2.  The Optional Metadata . . . . . . . . . . . . . . . . . .   4
       2.2.1.  URLs  . . . . . . . . . . . . . . . . . . . . . . . .   4
       2.2.2.  Content Type  . . . . . . . . . . . . . . . . . . . .   4
       2.2.3.  Experimental Metadata . . . . . . . . . . . . . . . .   5
   3.  Hashlink Serialization  . . . . . . . . . . . . . . . . . . .   5
     3.1.  Hashlink URL  . . . . . . . . . . . . . . . . . . . . . .   5
       3.1.1.  Serializing the Resource Hash . . . . . . . . . . . .   5
       3.1.2.  Serializing the Metadata  . . . . . . . . . . . . . .   6
       3.1.3.  Deserializing the Metadata  . . . . . . . . . . . . .   6
       3.1.4.  A Simple Hashlink Example . . . . . . . . . . . . . .   7
     3.2.  Hashlink as a Parameterized URL . . . . . . . . . . . . .   7
       3.2.1.  Hashlink as a Parameterized URL Example . . . . . . .   8
   4.  Hashlink Encoders and Decoders  . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
     5.1.  Insecure Hashing Functions  . . . . . . . . . . . . . . .   8
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     6.2.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Appendix A.  Security Considerations  . . . . . . . . . . . . . .   9
   Appendix B.  Test Values  . . . . . . . . . . . . . . . . . . . .   9
     B.1.  Simple Hashlink URL . . . . . . . . . . . . . . . . . . .   9
     B.2.  Multi-sourced Hashlink URL  . . . . . . . . . . . . . . .  10
   Appendix C.  Acknowledgements . . . . . . . . . . . . . . . . . .  10
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Uniform Resource Locators (URLs) enable software developers to build
   distributed systems that are able to publish information using
   hyperlinks.  When a client fetches a resource at the given hyperlink,