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www. oasis-open. org Practical Digital Signature Issues. Paving the way and new opportunities. Juan Carlos Cruellas – DSS-X co-chair Stefan Drees - DSS-X co-chair Marta Cruellas, CATCERT Pim van der Eijk, Sonnenglanz Consulting Detlef Huehnlein, Fed. Ministry of the Interior, Germany Ezer Farhi, ARX Andreas Kuehne Konrad Lanz, Austria Federal Chancellry Clements Orthacker. , A-SIT, Zentrum fur sichere Informationst
n Paving the way (I): l OASIS DSS Standards. Protocols for central services providing signature generation AND verification. n n n Avoid problems of deployment of infrastructure required to support individual generation All the complexity of verification implemented and deployed once at the server. Reduces overhead of key management: the central server takes care of the required tasks on certs status in both generation and verification. All the details of the policy for the signatures centralized. May keep logs of the verification processes and results.
DSS concept. Conventional approach n n n Deploy key to each user Handle Interface to all PKI functions Security depends on user
DSS concept. DSS approach Internal user Authentication & authorisation Directory System DSS Server PKI Certificate Management
DSS also forms the basis for the emerging standard e. ID-framework new classical DSS-domain DSS (X) http: //www. eid-stork. eu/ ISO/IEC 24727 / CEN TS 15480 („European Citizen Card“) ?
n n n OASIS Digital Signature Services TC produced a set of OASIS standards, including the core protocols and a number of profiles. When IPR modes changed, it was closed. New OASIS Digital Signature Services e. Xtended TC created operating under OASIS RF IPR mode.
l Ebxml Messaging Transport Binding for DSS. n n l Profile for managing visible signatures. n n l Specifies how DSS messages are encoded and carried using OASIS eb. XML Message Service (Ebxml MS: transport mechanism for e-business ). Binding for robust channel between DSS clients and servers and ebxm features (i. e. asynchronous messaging). Need to display (mostly in signed documents) information on the digital signatures to human beings, parts of which may also be signed. Clients will instruct servers to incorporate this visual information in the created signatures. Servers will also verify this signed visual information. Profile for supporting centralized encryption/decryption. n n Aims at providing protocols for requesting centralized encryption/decryption operations (CMS and XML Encryption). Combination of encryption and signature.
n l Profile for detailed individual verification reports. n l n Aims at allowing to DSS clients to request that the verification response is actually signed by the verifying server. Responses that may be seen as signed receipts of the verification of a certain signed document Profile for handling signature policies. n n l Individually report on each signature found in a document and incorporation in each one relevant details of the verification process, satisfying the business requirement of logging them. Profile for signed verification responses. n l Features: encryption/decryption of ¡parts of a document, encryption for different recipients, etc. Request generation/verification of a digital signature following a certain set of rules (signature policy). Different documents may require different types of signatures, generated and verified following different rules and processes. Analysis of inter-relationships among existing profiles.
n Paving the way (II): Interoperability events: l l Standards more and more complex. Interoperability is an issue. Interoperability tests: n n l l Face to face: XML Sec maintenance WG in 2007. BUT now ALSO REMOTE interoperability events. n n l Very useful for progressing towards interoperability. Provide feedback to the Standardization Bodies from actual implementers, helping in getting better standards (identify wrong or ambiguous parts, identify new requirements, etc). ETSI owns a portal supporting remote interoperability tests on XAd. ES signatures. It has conducted two Remote Interoperability events on XAd. ES (high figures of participation from Europe and Asia) and organized a third one for next year on XAd. ES and CAd. ES. See details at http: //xades-portal. etsi. org/pub/XAd. ES. shtml Also former DSS TC organized a restricted interoperability test between the TC members.
n New coming areas for digital signatures include trusted services supporting electronic business, with specific requirements on the signatures. Some examples: l l “Registered Electronic Mail”. ETSI is about to publish its Technical Specification TS 102 640: “Registered Electronic Mail (REM): Architecture, Formats and Policies”. http: //portal. etsi. org/stfs/STF_Home. Pages/STF 318. asp REM: an “ enhanced form of mail transmitted by electronic means (e-mail) which provides evidence relating to the handling of an e-mail including proof of submission and delivery “. TS: specifies generic architecture for the provision of this type of services, proposals formats of signed evidences and requirements on the corresponding digital signatures. It also acknowledges the existence of centralized services for generation and verification of digital signatures for evidences (DSS set of protocols). Signatures in relevant documents formats: new ETSI STF-364 on PDF signatures and Advanced Electronic Signatures (XAd. ES and CAd. ES). Among other things, it will profile CAd. ES and XAd. ES with the objective of using them for long term signatures within PDF documents framework