XML Evidence Record Syntax XMLERS v06 update and further steps 78th IETF Meeting, Maastricht

Agenda Overview Current status and specs Further steps and wrapup LTANS, 78th IETF, Maastrich, July 2010

Overview XMLERS Evidence Record Syntax representation in XML format  long term demonstration of data integrity based on time stamping Structure and processing instructions distinction from ASN.1 ERS representation (!) Hash values calculation require XML normalization (canonicalization) Repeating XML sibling elements have no natural order  need for order indicating attributes Embedded binary data must be encoded into XML compliant characters (base64) LTANS, 78th IETF, Maastrich, July 2010

Overview XMLERS Hash treeing Based on Merkle hash treeing Optimization of time-sptaming infrastructure/process Part of archive time stamp element No general rule for hash tree composition except for archive data object group  has values of archive data object present the initial list of hash values Might be used for time stamp renewal  hash tree input values presented by time stamp tokens of several ERSs LTANS, 78th IETF, Maastrich, July 2010

Hash treeing LTANS, 78th IETF, Maastrich, July 2010

Structure General structure Sequence of chains of archive time-stamps ATS1 ATS2 ATS3 ATSn Archive Time Stamp Chain 1 same digest algorithm ... protecting previous chain ATS1 ATS2 ATSm Archive Time Stamp Chain 2 ... ... ATS1 ATS2 ATSk Archive Time Stamp Chain 1 ... LTANS, 78th IETF, Maastrich, July 2010

Structure Archive time-stamp structure Time-Stamp Hash-Tree (optional) Time-Stamp Token RFC 3161 – base64 encoded XMLEntrust CryptographicInformationList (optional) CERT, CRL, OCSP – base 64 encoded Hash-Tree (optional) Unambiguous relationship between time-stamped value and protected data, created as reduced tree from (Merkle) hash tree Attributes (optional) LTANS, 78th IETF, Maastrich, July 2010

Structure XML structure <EvidenceRecord Version> <EncryptionInformation /> ? <ArchiveTimeStampSequence> <ArchiveTimeStampChain Order> <DigestMethod /> <CanonicalizationMethod /> <ArchiveTimeStamp Order> <HashTree /> ? <TimeStamp> <TimeStampToken Type /> <CryptographicInformationList /> ? </TimeStamp > <Attributes /> </ArchiveTimeStamp> + </ArchiveTimeStampChain> + </ArchiveTimeStampSequence> </EvidenceRecord> LTANS, 78th IETF, Maastrich, July 2010

Processes ERS Generation Compute hash value for archive data object When consisted of more data chunks /or/ a group process is performed, create a (Merkle) hash-tree and calculate the root hash Obtain time-stamp for (root) hash value Create <ArchiveTimeStamp> element composed of: <ArchiveTimeStamp Order=1> <HashTree> <Sequence Order=1> <DigestValue>qZk+NkcGgWq6PiVxeFDCbJzQ2J0=</DigestValue> <DigestValue>AZkBNkcGgW...</DigestValue> </Sequence> </ HashTree> <TimeStamp><TimeStampToken Type="RFC3161"> MIAGCSqGSI...</ TimeStampToken > </TimeStamp> <ArchiveTimeStamp> LTANS, 78th IETF, Maastrich, July 2010

Processes ERS Renewal Simple (using same hash algorithms) Collect cryptografic information for the last time-stamp token Calculate hash value for that time-stamp element Optionally (group process) create hash values for all time-stamps to be renewed and generate (Merkle) hash tree Obtain time-stamp for (root) hash value Create an archive-time stamp within the current chain LTANS, 78th IETF, Maastrich, July 2010

Processes ERS Renewal Complex (using new hash algorithms) Collect cryptografic information for the current time-stamp Calculate hash value for the complete sequence and archive data objects with the new algorithm Optionally (group process) create hash values for all time-stamps to be renewed and generate a (Merkle) hash tree Obtain time-stamp for the (root) hash value Create a new chain and the initial archive-time stamp within that chain (with a reduced hash-tree) LTANS, 78th IETF, Maastrich, July 2010

Status Current (stable) version 06 Optimization of elements use and structuring Renewal processes supported Initial and ERS grouping supported Time stamp format independency Cryptographic information = validation data (CRLs, OCSPs, X.509…) At least two independent implementations and several (at least 5) end user implementations LTANS, 78th IETF, Maastrich, July 2010

Further work Needs to be done Canonicalization methods! Some (important) typos Supported methods (some problems with namespaces might arise when using XML interpretation of time stamp tokens) General structure change Redefine time stamp element structure Add time stamp token (e.g. RFC3161 or XML-TS) Move crypto information into time stamp element resolve the issue with re-timestamping of the whole tree structure LTANS, 78th IETF, Maastrich, July 2010

Further work Further steps New version 07 due Last call Mid August End of August LTANS, 78th IETF, Maastrich, July 2010

Questions SETCCE Tehnološki park 21 Ljubljana Slovenia +386 1 6204500 info@setcce.si www.setcce.si LTANS, 78th IETF, Maastrich, July 2010