ERS to XML Introduction to ERS syntax in XML format 68th IETF meeting, Prague, March 2007

Introduction ERS syntax ASN.1 vs XML format XML processing rules Next steps Other March 2007 68th IETF Meeting,Prague

ERS ASN.1 Syntax Overview Syntax information – container for Long term demonstration of Data integrity Data time existence Based on Time stamp / Time stamp chains Hash trees ERS ASN.1 general overview Version Digest Algorithms Algorithm Identifier, Cryptographic Information Encryption Information Archive Time Stamp Sequence → Archive Time Chain → Archive Time Stamp March 2007 68th IETF Meeting,Prague

ERS ASN.1 Syntax Overview Archive Time Stamp Digest Algorithm Attributes Reduced Hash Tree Partial Hash Tree Sequence of (ordered) octet strings Archive Time Stamp Sequence Sequence of Archive Time Stamp Chain Sequence of Archive Time Stamp March 2007 68th IETF Meeting,Prague

ERS ASN.1 Syntax overview Encryption Information Sequence of Encryption Information Type and Encryption Information Value March 2007 68th IETF Meeting,Prague

ERS in XML format Structure Version Archive Time Stamp (+Order) Digest Method used for hash / hash trees Hash Tree (optional) Content Time Stamp Complementary Data (optional) March 2007 68th IETF Meeting,Prague

ERS in XML format Digest Method → reference to digest method algorithm URI Time Stamp structure → any (RFC3161 or Entrust XML Time Stamp Schema) Complementary Data → replaces cryptographic information (in ASN.1) Hash Trees → collection of significant values of protected objects (input objects and generated evidence within archival period) March 2007 68th IETF Meeting,Prague

ERS in XML Differences Hash values (of e.g. hash trees) Pros Cons Calculated only for the objects (not of ERS XML structures which hold those objects) When needed to bind many objects with single significant value → hash values of objects are sorted, concatenated and hashed Pros Hashes of protected items do not depend on specific ERS-XML structures, used to hold them Cons Not in the line with ERS-ASN.1 draft, where for the purpose of renewal hashes are calculated from the specifically formatted objects (order etc.) March 2007 68th IETF Meeting,Prague

ERS in XML Differences Simplified structure Pros Cons No structure for Sequences and Chains → only ordered sequence of Archive Time-stamps (ATS) Pros Simplified processing rules for generation and verification Cons Not in the line with ERS-ASN1 draft, where a first ATS in a chain holds ATS, created by the complex renewal process and others created by simple renewal process; March 2007 68th IETF Meeting,Prague

ERS in XML format Next steps Confirm general structure and procedures New version ready as of May 2007 Implementations and cross evaluation March 2007 68th IETF Meeting,Prague

General information Prepared by Aleksej Jerman Blazic Svetlana Saljic Tobias Gordon March 2007 68th IETF Meeting,Prague