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[GNUnet-developers] Fwd: address@hidden: ACISP02-status-yes]

From: Christian Grothoff
Subject: [GNUnet-developers] Fwd: address@hidden: ACISP02-status-yes]
Date: Mon, 1 Apr 2002 10:24:55 -0500

Hi guys!

Here are the reviews for the Anonymioty paper... 
Let's party!


----------  Forwarded Message  ----------
Subject: address@hidden: ACISP02-status-yes]
Date: Mon, 1 Apr 2002 21:54:28 +1000
From: Jennifer Seberry <address@hidden>
To: address@hidden, Jennifer Seberry <address@hidden>

Dear Dr Christian Grothoff and Co-authors

I am very happy to tell you that your paper acisp0263
Efficient Sharing of Encrypted Data
has been accepted by the committee.

I enclose the referees comments.

Referee 1:
Score: 5
Weight: 1
Comments to authors: Distributing file sharing might be useful because
network OS is developing now.

Referee 2:
Rating: 7
Confidence: 2

This paper describes a distributed file sharing protocol which breaks
up files and stores redundant copies of the partial files, in a
manner such that the server storing the parts cannot know what they
contain. The files can subsequently be located and reconstructed
using a keyword search.

I like the fact that this paper presents a clear progression from
design criteria to implementation details to analysis, and clearly
contrasts other approaches.

I have a question I couldn't answer from reading the paper. Are the
different types of Gblocks distinguishable in their encrypted form?
If they were, it seems to me that a particular system could run a
dictionary attack on the keyword-encoded RBlocks that it received,
and then refuse RBlocks that matched its ``naughty words'' list, then
in turn refuse blocks that are part of the corresponding files. This
dictionary attack applies whether or not the RBlocks are
distinguishable, but is probably more expensive if it has to be
applied to each of the data blocks too. Actually, I've just realised
that isn't true (it isn't more expensive), because there is no
variation in the keyword-encrypted RBlocks, so such a machine merely
has to have a list of H(H(K)) values and their corresponding ``dirty
keywords'' for which it will refuse to store the $R_K$, and when it sees
such an $R_K$, it can decrypt it, and search-and-destroy any component
Gblocks for such a file. This doesn't defeat the
censorship-resistance because a server might still store parts of a
file without ever seeing the corresponding RBlock to block it.

On page 2, ``asses'' should be ``assess''

In Figure 1, the GNUnet/network overhead box is blank, even though
the surrounding text gives good  figures for this. Surely it should
be ``approx 1''.

On page 11, just before 4.5 you say ``any other bit'' -- given the
context where we are talking about hash functions and so on, I found
this confusing, and feel that it might be better to say ``any other
GBlock'' here.

Referee 3:
Score: 5
Weight: 1

Comments authors:
This paper studies the GNUnet file-sharing protocol which supports
dissemination and queries over encrypted data.
This is an interesting topic. However, the authors are apparently not aware
 of the  paper: Practical Techniques for Searches on Encrypted Data (by Dawn
 Song, David
Wagner and Adrian Perrig) appeared in 2000 IEEE Symposium on Research in
Security and Privacy, which addresses the similar problem.

The final version is due in .ps or .pdf before 29th April if possible.

Best wishes
Jennifer Seberry

Professor of Computer Science
Director, Centre for Computer Security Research, TITR
Leader, Intelligent Environments Program, CRC for Smart Internet Technologies
School of Information Technology and Computer Science
University of Wollongong
NSW 2522, Australia

E-mail: address@hidden
Phone: +61 2 42 21 3606 (School)
Phone: +61 2 42 21 4327 (Centre)
Fax:   +61 2 42 21 4329

Program Co-Chair, ACISP'02

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|Christian Grothoff                                  |
|650-2 Young Graduate House, West Lafayette, IN 47906|
|   address@hidden|
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echo -e "\n\n\t\tMay the source be with you.\n\n"

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