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revision 1.28 by benja, Mon Oct 27 19:41:04 2003 UTC revision 1.29 by benja, Mon Oct 27 20:58:44 2003 UTC
# Line 48  if the shoulders keep rotting away? Line 48  if the shoulders keep rotting away?
48     have lost interest.>>>     have lost interest.>>>
49    
50  We don't propose that every byte of information ever published  We don't propose that every byte of information ever published
51  on the Web should have to be kept around forever. However,  on the Web has to be kept around forever. However,
52  we do believe that as long as someone does keep a copy,  we do believe that as long as someone does keep a copy,
53  data should remain accessible, and links should continue  data should remain accessible, and links should continue
54  to work.  to work.
# Line 65  a server name by location-independent, s Line 65  a server name by location-independent, s
65  like cryptographic hashes.  like cryptographic hashes.
66  A file identified by a cryptographic hash  A file identified by a cryptographic hash
67  can be downloaded from any server that has a copy; the client  can be downloaded from any server that has a copy; the client
68  can then check it is the correct file by checking the hash.  can then check the integrity of the file by checking it against the hash.
69    
70  .. <<<Self-verifying means that given the identifier and a file,  .. <<<Self-verifying means that given the identifier and a file,
71     a client can check that the file matches the identifier.>>>     a client can check that the file matches the identifier.>>>
# Line 78  using location-independent identifiers Line 78  using location-independent identifiers
78  is not viable on a global scale:  is not viable on a global scale:
79  "[I]f you put information in a name, it decreases its longevity;  "[I]f you put information in a name, it decreases its longevity;
80  if you don't you can't dereference it to a resource."  if you don't you can't dereference it to a resource."
81  However, as we have observed in [fallenstein03storm]_,  
82  with the advent of  However, as observed in [fallenstein03storm]_,
83  efficient peer-to-peer lookup mechanisms such as  with the advent of efficient peer-to-peer lookup mechanisms such as
84  distributed hashtables (DHTs), this observation  distributed hashtables (DHTs), this observation
85  is no longer true.  is no longer true. A DHT is quite able to resolve a
86    hash-based identifier on a global scale,
87    as evidenced by applications like the Cooperative
88    File System (CFS, [dabek01widearea]_) and
89    the Overnet file sharing client [overneturl]_.
90    
91    .. SFR (semantic-free referencing) not all that close,
92       though semantic-free idea shared (SFR takes along
93       many problems of the Web)
94    
95  Using DHTs  .. <<<(Using DHTs
96  to resolve location-independent identifiers on the Web     to resolve location-independent identifiers on the Web
97  has been proposed by Balakrishnan et.al.     has been proposed by Balakrishnan et.al.
98  [balakrishnan03semanticfree-andalso-walfish03dns]_.     [balakrishnan03semanticfree-andalso-walfish03dns]_.
99       However, in their work, the location-independent identifier
100       merely points to a Web server administered by the publisher
101       of a Web page; if the original publisher discontinues
102       maintenance of the page, it would still drop off the Web.)>>>
103    
104  .. Proposal: A location-independent Web (closest thing is Freenet (ref))     XXX move to related work?
105    
106    .. Proposal: A location-independent Web <<<(closest thing is Freenet (ref))>>>
107    
108  We propose, then, to build a location-independent Web  We propose, then, to build a location-independent Web
109  based on self-verifying identifiers.  based on self-verifying identifiers.
110    
111  The project that is currently closest to this goal is Freenet,  .. <<<The project that is currently closest to this goal is Freenet,
112  a XXX     a XXX>>>
113    
114  .. Benefits of hash-based addressing:  .. Benefits of hash-based addressing:
115     - Pages easily movable between servers     - Pages easily movable between servers
# Line 106  a XXX Line 120  a XXX
120     - Verifiable     - Verifiable
121     - Same namespace for local and for non-local data     - Same namespace for local and for non-local data
122    
123  .. SFR (semantic-free referencing) not all that close,  Using hash-based addressing in such a scheme has several benefits:
    though semantic-free idea shared (SFR takes along  
    many problems of the Web)  
124    
125  .. Other projects exploit some of the advantages of hash-based  - Pages can be moved between servers without breaking links.
126    - Links continue to work as long as *anybody* keeps a copy
127      of their targets, even if the original publisher does not
128      maintain the Web page any longer.
129    - Downloaded files can keep their global identifiers.
130      Links between two downloaded Web pages automatically work.
131    - It is possible to implement load-balancing schemes in which
132      a user downloads a page from anybody who happens to have a copy.
133    - Different networks can be used to download a file. XXX
134    
135    .. <<<Other projects exploit some of the advantages of hash-based
136     (storage systems: CFS, PAST; web caching: Squirrel),     (storage systems: CFS, PAST; web caching: Squirrel),
137     but don't address the Web.     but don't address the Web.>>>
138    
139  .. The infrastructure behind CFS, PAST and Squirrel: Peer-to-Peer  .. <<<The infrastructure behind CFS, PAST and Squirrel: Peer-to-Peer>>>
140    
141  .. Quite recently, several Peer-to-Peer architectures have been  .. <<<Quite recently, several Peer-to-Peer architectures have been
142     proposed that use hash-based, loc.ind. ids     proposed that use hash-based, loc.ind. ids>>>
143    
144  .. Possibility of desktop integration in ways that the location-dependent  .. Possibility of desktop integration in ways that the location-dependent
145     Web cannot archieve, through the novel combination of     Web cannot archieve, through the novel combination of
# Line 126  a XXX Line 148  a XXX
148  .. However, there's a problem with this: versioning -----  .. However, there's a problem with this: versioning -----
149     Basic problem: Hash-based addressing allows no updates     Basic problem: Hash-based addressing allows no updates
150    
151    However, a document refered to by a cryptographic hash
152    can obviously not be changed (without making it a different document,
153    refered to by a different hash). For most Web pages, this is not
154    acceptable [#academic-articles-hashlinking]_. In this paper,
155    we examine solutions to this problem that keep the desirable properties
156    of hash-based addressing.
157    
158  .. Contributions; structure of this paper ----  .. Contributions; structure of this paper ----
159    
160  .. Main contrib: Pointer records for implementing updating  .. Main contrib: Pointer records for implementing updating
161    
162    The main contribution of our paper are *pointer records*.
163    A document is identified by a *pointer*, the hash of a
164    public key. A pointer record is a file signed by the
165    corresponding private key, containing the pointer's identity,
166    the hash of a version of that document, and a timestamp.
167    The newest version of a document is obtained by searching
168    the peer-to-peer network for all pointer records associated
169    with this pointer, and picking the newest one.
170    
171    This scheme is quite close to OceanStore's concept of
172    *heartbeats*. However, the difference is that in OceanStore,
173    heartbeats are controlled by an inner circle of servers,
174    the *primary replica*, chosen by the owner of the document.
175    In this scheme, when a document ceases to be maintained
176    by its primary replica, it is impossible/becomes harder/*what*?XXX
177    to retrieve the newest version of the document.
178    
179    (XXX IS THIS TRUE?)
180    
181  .. Other contribs:  .. Other contribs:
182     - The idea of a location-independent Web including     - The idea of a location-independent Web including
183       location-independent version management       location-independent version management
184     - Diffs     - Diffs
185       - Permanent signature scheme sketch
186    
187    In addition to pointer records, this paper XXX
188    
189    .. Structure of this paper
190    
191    The remainder of this paper is structured as follows.
192    In Section 2, we review related work in version management,
193    and find that existing peer-to-peer versioning systems
194    do not provide the benefits of hash-based addressing.
195    In Section 3, we introduce our fundamental, hash-based data model
196    for a location-independent Web. In Section 4, we propose
197    a versioning system built on top of this data model.
198    In Section 5, we introduce a scheme for storing only
199    the differences between versions that works with our
200    basic data model, making the storage of past versions
201    more economical. In Section 6, we outline solutions
202    to the permanency issues raised by the use of
203    cryptographic keys (which may be stolen or lost).
204    Section 7 concludes.
205    
206    
207    
208  Related work  Related work
# Line 305  Notes Line 374  Notes
374  .. [#rtg-links] ``http://www.seds.org/spaceviews/cassini/rtgpages.html``.  .. [#rtg-links] ``http://www.seds.org/spaceviews/cassini/rtgpages.html``.
375     All links dereferenced on October 27th, 2003.     All links dereferenced on October 27th, 2003.
376    
377    .. [#academic-articles-can-use-hashlinking] A notable exception
378       may be academic articles, in which references to other articles
379       are ideally to an immutable version, and in which references
380       are generally not circular, making this domain map neatly
381       to the properties of hash-based referencing.

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