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Long-term Archive And Notary                                  C. Wallace
Services (LTANS)                                Orion Security Solutions
Internet-Draft                                               U. Pordesch
Expires: November 1, 2004                        Fraunhofer Gesellschaft
                                                             R. Brandner
                                                   InterComponentWare AG
                                                             May 3, 2004


                 Long term archive service requirements
                      draft-ietf-ltans-reqs-01.txt

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on November 1, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2004). All Rights Reserved.

Abstract

   In many scenarios, users need to be able to ensure and prove the
   existence and integrity of data, especially digitally signed data, in
   a common and reproducible way over an arbitrarily long period. This
   document specifies the technical requirements for a long-term archive
   service to support such scenarios.







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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  General Principles . . . . . . . . . . . . . . . . . . . . . .  7
   4.  Technical Requirements . . . . . . . . . . . . . . . . . . . .  8
     4.1   Enable submission,retrieval and deletion . . . . . . . . .  8
     4.2   Provide evidence records . . . . . . . . . . . . . . . . .  9
     4.3   Support Demonstration of Data Integrity  . . . . . . . . .  9
     4.4   Operate per a long-term archive policy . . . . . . . . . .  9
     4.5   Data confidentiality . . . . . . . . . . . . . . . . . . . 10
     4.6   Data and evidence transferability  . . . . . . . . . . . . 10
     4.7   Supporting Groups of Data  . . . . . . . . . . . . . . . . 11
   5.  Operational Considerations . . . . . . . . . . . . . . . . . . 12
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 14
   A.  Application scenarios  . . . . . . . . . . . . . . . . . . . . 16
     A.1   Archive service supporting long-term non-repudiation . . . 16
     A.2   Pure long-term non-repudiation service . . . . . . . . . . 16
     A.3   Long-term Archive Service as part of an internal
           network  . . . . . . . . . . . . . . . . . . . . . . . . . 16
     A.4   Long-term Archive External Service . . . . . . . . . . . . 16
       Intellectual Property and Copyright Statements . . . . . . . . 17


























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1.  Introduction

   Digital data durability is undermined by continual progress and
   change on a number of fronts. The useful lifetime of data may exceed
   the life span of formats and mechanisms used to store the data.  The
   lifetime of digitally signed data may exceed the validity periods of
   public-key certificates used to verify signatures or the
   cryptanalysis period of the cryptographic algorithms used to generate
   the signatures. Technical and operational means are required to
   mitigate these issues.  A solution must address issues such as
   storage media lifetime, disaster planning, advances in cryptanalysis
   or computational capabilities, changes in software technology and
   legal issues.

   A long-term archive service aids in the preservation of data over
   long periods of time. For example, it might periodically perform
   activities to preserve data integrity and the non-reputability of
   data existence as well as ensuring the availability of data. Examples
   of periodic activities include refreshing timestamps or transferring
   data to a new storage medium.

   A long-term archive service may be used to support validation of the
   existence of documents, or assertions of agreements, originally
   asserted with digital signatures.  Validation may occur at times in
   the future well beyond the validity period of the private key
   originally used to generate the signature, or even the validity of
   the algorithms available for digital signatures, message digesting or
   data encryption.

   A long-term archive service may be located within an enterprise
   network, communicating with local storage mechanisms and other
   applications, or a long-term archive service may be an external
   service accessible via internet.  A long-term archive service may use
   functionality, e.g. time stamping, provided by independent service
   providers.

   A primary goal of a long-term archive service is to support the
   credible assertion of something that is currently asserted at points
   well into the future.  A long-term archive service may support a
   range of applications, including: wills, land records, medical data,
   criminal case files, personnel files, contracts.  A long-term archive
   service may be used by any type of entity, e.g. organizations,
   citizens, notaries.  Examples of long-term archive service usage by
   submitters include:

      - A company stores contracts using a third party service
      - A hospital stores medical data using an internal service




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      - An individual wants to generate evidence of data possession at a
      particular point in time, e.g. for intellectual property purposes
      or endorsement of a contract
      - A law enforcement officer wants to store criminal data such that
      integrity of the data can be demonstrated years later


   For each of the above examples, there is a corresponding example
   involving retrievers, e.g. a company retrieves a contract in the case
   of a dispute or a law enforcement officer assembles information for a
   criminal trial.

   This document aims to identify the technical requirements for a
   long-term archive service. The requirements for long-term
   notarization services will be covered by a separate draft.




































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2.  Terminology


      Arbitrator: Principal for whom the validity of archived data
      characteristics, e.g., origin, integrity or time of existence,
      must be demonstrated.

      Archivation period: The period during which an archived data
      object is preserved by a long-term archive service.

      Archived data object: Data unit to be preserved by a long-term
      archive service.

      Archive package: Collection of information including archived data
      objects and associated evidence record.

      Evidence: Information that may be used to demonstrate the validity
      an archived data object or related attestations.

      Evidence record: Collectionof evidence compiled for one or more
      archived data objects. An evidence record may include
      acknowledgements of TAA, timestamps and verification data, such as
      public-key certificates, revocation information, trust anchors,
      policy details and role information.

      Long-term archive policy: A named set of rules that define
      operational characteristics of a long-term archive service.

      Long-term archive service: See Trusted Archive Authority.

      Originator: Principal who produces, and possibly signs, an
      archived data object.The Originator does not necessarily have any
      relationship with a long-term archive service or any awareness of
      an evidence record associated with the archived data object.

      Retriever: Principal who retrieves an archived data objects and/or
      evidence record from a long-term archive service.

      Submitter: Principal who submits data objects for archiving.

      Timestamp: A signed attestation generated by a Time Stamping
      Authority (TSA) that a data item existed at a certain
      time.[RFC3161] specifies a structure for timestamps and a protocol
      for communicating with a Timestamp Authority (TSA).

      Time Stamping Authority (TSA): A service that generates
      timestamps.




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      Trusted Archive Authority (TAA): A service that is responsible for
      preserving data for long periods.
















































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3.  General Principles

   A long-term archive service may accept any type of data for
   preservation, including digitally signed data, encrypted data, time
   stamped data, data that has not been the subject of any cryptographic
   processing, textual data or images.

   A long-term archive service may preserve archived data objects as
   opaque collections of bytes with the primary aim being demonstration
   of data integrity.

   A long-term archive service does not collect evidence related to the
   content of archived data objects.Content-focused operations,
   including data format migration or translation, may be performed by a
   notary or notarization service.

   A long-term archive service stores archived data objects over
   arbitrarily long periods of time.

   A long-term archive service provides material needed to demonstrate
   the existence and integrity of data objects.






























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4.  Technical Requirements

   This section describes requirements for a long-term archive system.

4.1  Enable submission,retrieval and deletion

4.1.1  Functional Requirements

   A long-term archive service must permit clients to perform the
   following basic operations:

      - submit data
      - retrieve data,
      - delete data/terminate archivation period.

   Submitters must be able to specify an archivation period.  It should
   be possible to extend the archiving period. Submitters should be able
   to specify metadata that, for example, can be used to provide enable
   retrievers to render the data correctly.

   Following submission, the service must provide a value that can be
   used to retrieve the archived data and/or associated evidence. It may
   be possible to retrieve archive packages by using a hash value of the
   archived data objects.

   Deletion requests must be authorized and an authorization policy must
   be defined and observed by the long-term archive service (as part of
   an archive policy). In some cases, deletion may not involve physical
   deletion and instead may simply be an early termination of the
   archivation period.

   It must be possible to authenticate requests and responses.  This may
   be accomplished using transport security mechanisms.

   The format for the acknowledgements must allow the identification of
   the archiving provider.

   The format for the acknowledgements must allow the identification of
   the participating client.

   The acknowledgement of a successful submission should permit the
   submitter to verify that the correct data was received by the service
   for preservation, e.g. the acknowledgement could include an index, a
   signature or a timestamp obtained for the archived data object.

4.1.2  Rationale

   Submission, retrieval and deletion of archived data are necessary



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   basic functions of a long-term archive service.

4.2  Provide evidence records

4.2.1  Functional Requirements

   A long-term archive service must be capable of providing evidence
   records to support the long-term non-repudiation of data, e.g. in the
   case of legal disputes.

   It must be possible to submit data along with previously generated
   evidence, i.e. to support transfer of data from one archive to
   another. Submitters must be able to specify metadata that, for
   example, can be used to provide enable retrievers to render the data
   correctly.

4.2.2  Rationale

   Supporting non-repudiation of data is the primary purpose of a
   long-term archive service.  Evidence may be generated by or otherwise
   obtained by the service providing them to a retriever. A long-term
   archive service need not be capable of providing all evidence
   necessary to produce a non-repudiation proof. In particular, trust
   anchors and algorithm security policies have to be provided by other
   services.

4.3  Support Demonstration of Data Integrity

4.3.1  Functional Requirements

   A longterm archive service must be capable of producing evidence that
   can be used to demonstrate the integrity of data for which it is
   responsible from the time it received the data until the expiration
   of the archivation period of the data.

4.3.2  Rationale

   Demonstration that data has not been altered while in the care of a
   long-term archive service is a first step towards supporting
   non-repudiation of data.  Content-focused operations will be the
   function of a notarization service.

4.4  Operate per a long-term archive policy

4.4.1  Functional Requirements

   A long-term archive service must operate per a long-term archive
   service policy that defines characteristics of the implementation of



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   the long-term archive service. The policy may define characteristic
   such as the quality of timestamps obtained or generated by the
   long-term archive service or triggers for preservation activities,
   e.g. timestamp refresh or data format migration.

   A long-term archive service must be able to provide information
   identifying the policies in use at any point in time. Submitters must
   be able to indicate the archive policy under which the submitted data
   should be handled. The service must provide an indication of the
   archive policy observed by the service. If a long-term archive
   service does not support a client-requested policy, it must return an
   error indication.

4.4.2  Rationale

   Similar to a certificate policy, a long-term archive policy provides
   a shorthand means of technically expressing a set of rules that
   govern operation of a long-term archive service.

4.5  Data confidentiality

4.5.1  Functional Requirements

   A long-term archive service must provide means to ensure
   confidentiality of archived data objects, including confidentiality
   between the submitter and the long term archive service.

   Traditional standardized encrypting methods and formats, e.g. CMS,
   should be supported.

   The concept should be open to add other methods for confidentiality,
   like sharing secrets between different archive providers

   Encryption or other methods must not pose a risk to evidence.

4.5.2  Rationale

   Individuals may wish to use the services of a commercial long-term
   service without disclosing data to the commercial service.

4.6  Data and evidence transferability

4.6.1  Functional Requirements

   A long-term archive service must support the transfer of archived
   data objects, evidence and evidence records from one service to
   another.




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4.6.2  Rationale

   Before the end of an archived data object's archivation period, a
   long-term archive service may cease operation. In such cases, it must
   be possible for the archived data object (and any associated
   evidence) to be transferred to another service that will continue
   preservation of the data until the end of the archivation period.

4.7  Supporting Groups of Data

4.7.1  Functional Requirements

   The service should support groups of data objects.

   Submitters should be able to indicate which data objects belong
   together, i.e. comprise a group. Retrievers should be able to
   retrieve all members of a group of data objects.

   It should be possible to provide evidence for groups of archived data
   objects.  For example, it should be possible to archive a document
   file and a signature file together such that they are covered by the
   same evidence record.

   Where groups of data objects are submitted, non-repudiation proof
   must still be available for each archived data object separately.

4.7.2  Rationale

   In many cases data objects belong together. Examples include:

   - a document file and an associated signature file, which are two
   separate objects

   - TIF-files representing pages of a document

   - a document file and an evidence file (possibly generated by another
   TAA or notary service)

   In these cases, it is to the best advantage to handle these data
   objects as a group.











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5.  Operational Considerations

   A long-term archive service must be able to work efficiently even for
   large amounts of archived data objects. In order to limit expenses
   and to achieve high performance, the involvement of trusted third
   parties should be minimized.

   Necessity to access archived data objects should be minimized. It may
   only be necessary access to the archived data objects if the archived
   data objects are requested by users or if hash algorithms used for
   indexing or evidence record generation become insecure.








































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6.  Security Considerations

   Data is the principal asset protected by a long-term archive service.
   The principle threat addressed by a long-term archive service is
   undetected loss of data integrity.

   Certificate revocation could retroactively invalidate previously
   verified signatures.  Measures may be implemented to support such
   claims by an alleged signer, e.g. collection of revocation
   information after a grace period during which compromise can be
   reported or preservation of subsequent revocation information.

   Access control mechanisms associated with data stored by a TAA should
   consider the lifespan of the data object.  For example, the
   credentials of an entity that submitted data to an archive may not be
   available or valid when the data needs to be retrieved.

   During archiving period data format may not be no longer supported.
   Software components to process data, its content or signatures, may
   no longer available, in particular if non-standard formats are used
   or proprietary processing is employed. Submitter has to take care
   about this potential problem. E.g. he has to retrieve data in time,
   convert them and re-submit it in new format. Of course additional
   mechanisms, applications or tools are needed in order to conserve
   evidence value. Other specifications of LTANS, in particular to
   notary services will adress these problems.

























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7.  Acknowledgements

   Thanks to members of the LTANS mailing list for review of earlier
   drafts and many suggestions.

8  References

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, October 1996.

   [RFC2028]  Hovey, R. and S. Bradner, "The Organizations Involved in
              the IETF Standards Process", BCP 11, RFC 2028, October
              1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3029]  Adams, C., Sylvester, P., Zolotarev, M. and R. Zuccherato,
              "Internet X.509 Public Key Infrastructure Data Validation
              and Certification Server Protocols", RFC 3029, February
              2001.

   [RFC3161]  Adams, C., Cain, P., Pinkas, D. and R. Zuccherato,
              "Internet X.509 Public Key Infrastructure Time-Stamp
              Protocol (TSP)", RFC 3161, August 2001.


Authors' Addresses

   Carl Wallace
   Orion Security Solutions
   Suite 300
   1489 Chain Bridge Road
   McLean, VA  22101

   Fax:   +1(703)917-0260
   EMail: cwallace@orionsec.com


   Ulrich Pordesch
   Fraunhofer Gesellschaft
   Dolivostrasse 15
   Darmstadt, Germany  D-64293

   EMail: ulrich.pordesch@zv.fraunhofer.de






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   Ralf Brandner
   InterComponentWare AG
   Otto-Hahn-Strabe 3
   Walldorf, Germany  69190

   EMail: ralf.brandner@intercomponentware.com













































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Appendix A.  Application scenarios

   Below are several example application scenarios providing one or more
   of the basic service features mentioned above.

A.1  Archive service supporting long-term non-repudiation

   A long-term archive service may store data objects, like signed or
   unsigned documents, for authenticated users.  It may generate time
   stamps for these data objects and obtain verification data during the
   archivation period or until a deletion request is received from an
   authorized entity.

A.2  Pure long-term non-repudiation service

   A long-term archive service may only guarantee non-repudiation of
   existence of data by periodically generating time stamps and
   obtaining verification data.  It stores data objects (e.g. documents
   and signatures) locally only for the purpose of non-repudiation and
   does not function as a document archive for users.  It does not
   support retrieval and deletion of data objects.

A.3  Long-term Archive Service as part of an internal network

   A long-term archive service may be part of an enterprise network.
   The network provider and archive provider may be the same
   institution.  In this case, the provider will use an external TSA, to
   generate non-repudiation evidence from a third party.  An internally
   generated acknowledgement would be worthless.

A.4  Long-term Archive External Service

   A long-term archive service may be provided over the internet for
   enterprises or consumers. In this case, archiving and providing
   evidence (via time-stamps or other means) may be adduced by one
   organisation and its own technical infrastructure without using
   external services.














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Intellectual Property Statement

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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgment

   Funding for the RFC Editor function is currently provided by the
   Internet Society.











































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