<h3>Entries from June 2017.</h3>
+ <div class="entry">
+ <div class="title">
+ <a href="http://people.skolelinux.org/pere/blog/Idea_for_storing_trusted_timestamps_in_a_Noark_5_archive.html">Idea for storing trusted timestamps in a Noark 5 archive</a>
+ </div>
+ <div class="date">
+ 7th June 2017
+ </div>
+ <div class="body">
+ <p><em>This is a copy of
+<a href="https://lists.nuug.no/pipermail/nikita-noark/2017-June/000297.html">an
+email I posted to the nikita-noark mailing list</a>. Please follow up
+there if you would like to discuss this topic. The background is that
+we are making a free software archive system based on the Norwegian
+<a href="https://www.arkivverket.no/forvaltning-og-utvikling/regelverk-og-standarder/noark-standarden">Noark
+5 standard</a> for government archives.</em></p>
+
+<p>I've been wondering a bit lately how trusted timestamps could be
+stored in Noark 5.
+<a href="https://en.wikipedia.org/wiki/Trusted_timestamping">Trusted
+timestamps</a> can be used to verify that some information
+(document/file/checksum/metadata) have not been changed since a
+specific time in the past. This is useful to verify the integrity of
+the documents in the archive.</p>
+
+<p>Then it occured to me, perhaps the trusted timestamps could be
+stored as dokument variants (ie dokumentobjekt referered to from
+dokumentbeskrivelse) with the filename set to the hash it is
+stamping?</p>
+
+<p>Given a "dokumentbeskrivelse" with an associated "dokumentobjekt",
+a new dokumentobjekt is associated with "dokumentbeskrivelse" with the
+same attributes as the stamped dokumentobjekt except these
+attributes:</p>
+
+<ul>
+
+<li>format -> "RFC3161"
+<li>mimeType -> "application/timestamp-reply"
+<li>formatDetaljer -> "<source URL for timestamp service>"
+<li>filenavn -> "<sjekksum>.tsr"
+
+</ul>
+
+<p>This assume a service following
+<a href="https://tools.ietf.org/html/rfc3161">IETF RFC 3161</a> is
+used, which specifiy the given MIME type for replies and the .tsr file
+ending for the content of such trusted timestamp. As far as I can
+tell from the Noark 5 specifications, it is OK to have several
+variants/renderings of a dokument attached to a given
+dokumentbeskrivelse objekt. It might be stretching it a bit to make
+some of these variants represent crypto-signatures useful for
+verifying the document integrity instead of representing the dokument
+itself.</p>
+
+<p>Using the source of the service in formatDetaljer allow several
+timestamping services to be used. This is useful to spread the risk
+of key compromise over several organisations. It would only be a
+problem to trust the timestamps if all of the organisations are
+compromised.</p>
+
+<p>The following oneliner on Linux can be used to generate the tsr
+file. $input is the path to the file to checksum, and $sha256 is the
+SHA-256 checksum of the file (ie the "<sjekksum>.tsr" value mentioned
+above).</p>
+
+<p><blockquote><pre>
+openssl ts -query -data "$inputfile" -cert -sha256 -no_nonce \
+ | curl -s -H "Content-Type: application/timestamp-query" \
+ --data-binary "@-" http://zeitstempel.dfn.de > $sha256.tsr
+</pre></blockquote></p>
+
+<p>To verify the timestamp, you first need to download the public key
+of the trusted timestamp service, for example using this command:</p>
+
+<p><blockquote><pre>
+wget -O ca-cert.txt \
+ https://pki.pca.dfn.de/global-services-ca/pub/cacert/chain.txt
+</pre></blockquote></p>
+
+<p>Note, the public key should be stored alongside the timestamps in
+the archive to make sure it is also available 100 years from now. It
+is probably a good idea to standardise how and were to store such
+public keys, to make it easier to find for those trying to verify
+documents 100 or 1000 years from now. :)</p>
+
+<p>The verification itself is a simple openssl command:</p>
+
+<p><blockquote><pre>
+openssl ts -verify -data $inputfile -in $sha256.tsr \
+ -CAfile ca-cert.txt -text
+</pre></blockquote></p>
+
+<p>Is there any reason this approach would not work? Is it somehow against
+the Noark 5 specification?</p>
+
+ </div>
+ <div class="tags">
+
+
+ Tags: <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="http://people.skolelinux.org/pere/blog/tags/offentlig innsyn">offentlig innsyn</a>, <a href="http://people.skolelinux.org/pere/blog/tags/standard">standard</a>.
+
+
+ </div>
+ </div>
+ <div class="padding"></div>
+
<div class="entry">
<div class="title">
<a href="http://people.skolelinux.org/pere/blog/N_r_nynorskoversettelsen_svikter_til_eksamen___.html">Når nynorskoversettelsen svikter til eksamen...</a>
<li><a href="http://people.skolelinux.org/pere/blog/archive/2017/04/">April (2)</a></li>
-<li><a href="http://people.skolelinux.org/pere/blog/archive/2017/06/">June (1)</a></li>
+<li><a href="http://people.skolelinux.org/pere/blog/archive/2017/06/">June (2)</a></li>
</ul></li>
<li><a href="http://people.skolelinux.org/pere/blog/tags/drivstoffpriser">drivstoffpriser (4)</a></li>
- <li><a href="http://people.skolelinux.org/pere/blog/tags/english">english (346)</a></li>
+ <li><a href="http://people.skolelinux.org/pere/blog/tags/english">english (347)</a></li>
<li><a href="http://people.skolelinux.org/pere/blog/tags/fiksgatami">fiksgatami (23)</a></li>
<li><a href="http://people.skolelinux.org/pere/blog/tags/nuug">nuug (188)</a></li>
- <li><a href="http://people.skolelinux.org/pere/blog/tags/offentlig innsyn">offentlig innsyn (31)</a></li>
+ <li><a href="http://people.skolelinux.org/pere/blog/tags/offentlig innsyn">offentlig innsyn (32)</a></li>
<li><a href="http://people.skolelinux.org/pere/blog/tags/open311">open311 (2)</a></li>
<li><a href="http://people.skolelinux.org/pere/blog/tags/skepsis">skepsis (5)</a></li>
- <li><a href="http://people.skolelinux.org/pere/blog/tags/standard">standard (52)</a></li>
+ <li><a href="http://people.skolelinux.org/pere/blog/tags/standard">standard (54)</a></li>
<li><a href="http://people.skolelinux.org/pere/blog/tags/stavekontroll">stavekontroll (6)</a></li>
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