ERS to XML Introduction to ERS syntax in

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

Introduction • • • ERS syntax ASN. 1 vs XML format XML processing rules Next steps Other

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

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

ERS ASN. 1 Syntax overview • Encryption Information – Sequence of Encryption Information Type and – Encryption Information Value

ERS in XML format • Structure – Version – Archive Time Stamp (+Order) • Digest Method used for hash / hash trees • Hash Tree (optional) – Content • Time Stamp – Content • Complementary Data (optional)

ERS in XML format • Digest Method → reference to digest method algorithm URI • Time Stamp structure → any (RFC 3161 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)

ERS in XML Differences • Hash values (of e. g. hash trees) • 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 ERSXML 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. )

ERS in XML Differences • Simplified structure • 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-ASN 1 draft, where a first ATS in a chain holds ATS, created by the complex renewal process and others created by simple renewal process;

ERS in XML format • Next steps – Confirm general structure and procedures – New version ready as of May 2007 – Implementations and cross evaluation

General information • Prepared by – Aleksej Jerman Blazic – Svetlana Saljic – Tobias Gordon