From aa4069048e4b39f85304deb4c9abc90695b8441c Mon Sep 17 00:00:00 2001 From: Petter Reinholdtsen Date: Wed, 7 Jun 2017 21:44:22 +0200 Subject: [PATCH] Generated. --- ...usted_timestamps_in_a_Noark_5_archive.html | 518 ++++++++++++++++++ 1 file changed, 518 insertions(+) create mode 100644 blog/Idea_for_storing_trusted_timestamps_in_a_Noark_5_archive.html diff --git a/blog/Idea_for_storing_trusted_timestamps_in_a_Noark_5_archive.html b/blog/Idea_for_storing_trusted_timestamps_in_a_Noark_5_archive.html new file mode 100644 index 0000000000..12ff673f5d --- /dev/null +++ b/blog/Idea_for_storing_trusted_timestamps_in_a_Noark_5_archive.html @@ -0,0 +1,518 @@ + + + + + Petter Reinholdtsen: Idea for storing trusted timestamps in a Noark 5 archive + + + + + + +
+

+ Petter Reinholdtsen + +

+ +
+ + +
+
Idea for storing trusted timestamps in a Noark 5 archive
+
7th June 2017
+

This is a copy of +an +email I posted to the nikita-noark mailing list. 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 +Noark +5 standard for government archives.

+ +

I've been wondering a bit lately how trusted timestamps could be +stored in Noark 5. +Trusted +timestamps 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.

+ +

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?

+ +

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:

+ +
    + +
  • format -> "RFC3161" +
  • mimeType -> "application/timestamp-reply" +
  • formatDetaljer -> "<source URL for timestamp service>" +
  • filenavn -> "<sjekksum>.tsr" + +
+ +

This assume a service following +IETF RFC 3161 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.

+ +

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.

+ +

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 ".tsr" value mentioned +above).

+ +

+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
+

+ +

To verify the timestamp, you first need to download the public key +of the trusted timestamp service, for example using this command:

+ +

+wget -O ca-cert.txt \
+  https://pki.pca.dfn.de/global-services-ca/pub/cacert/chain.txt
+

+ +

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. :)

+ +

The verification itself is a simple openssl command:

+ +

+openssl ts -verify -data $inputfile -in $sha256.tsr \
+  -CAfile ca-cert.txt -text
+

+ +

Is there any reason this approach would not work? Is it somehow against +the Noark 5 specification?

+
+ +
Tags: english, offentlig innsyn, standard.
+ + +
+ + + + + +

+ Created by Chronicle v4.6 +

+ + + -- 2.47.2