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ABFAB                                                      R. Smith, Ed.
Internet-Draft                                        Cardiff University
Intended status: Informational                        September 25, 2012
Expires: March 29, 2013


 Application Bridging for Federated Access Beyond web (ABFAB) Use Cases
                      draft-ietf-abfab-usecases-05

Abstract

   Federated identity is typically associated with Web-based services at
   present, but there is growing interest in its application in non Web-
   based contexts.  The goal of this document is to document a selection
   of the wide variety of these contexts whose user experience could be
   improved through the use of technologies based on the ABFAB
   architecture and specifications.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 29, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as



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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Context of Use Cases . . . . . . . . . . . . . . . . . . . . .  3
   3.  Use Cases  . . . . . . . . . . . . . . . . . . . . . . . . . .  3
     3.1.  Cloud Services . . . . . . . . . . . . . . . . . . . . . .  4
       3.1.1.  Cloud-based Application Services . . . . . . . . . . .  4
       3.1.2.  Cloud-based Infrastructure Services  . . . . . . . . .  5
     3.2.  High Performance Computing . . . . . . . . . . . . . . . .  6
     3.3.  Grid Infrastructure  . . . . . . . . . . . . . . . . . . .  7
     3.4.  Databases and Directories  . . . . . . . . . . . . . . . .  8
     3.5.  Media Streaming  . . . . . . . . . . . . . . . . . . . . .  8
     3.6.  Printing . . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.7.  Accessing Applications from Devices on a Telecoms
           Infrastructure . . . . . . . . . . . . . . . . . . . . . .  9
     3.8.  Enhanced Security Services for S/MIME  . . . . . . . . . . 10
     3.9.  Smart Objects  . . . . . . . . . . . . . . . . . . . . . . 11
   4.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 12

























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1.  Introduction

   Federated identity facilitates the controlled sharing of information
   about people (a.k.a. 'principals'), commonly across organisational
   boundaries.  This avoids redundant registration of principals who
   operate in and across multiple domains; both reducing the
   administrative overhead for the organizations involved and improving
   the usability of systems for the principal.  Simultaneously, it can
   also help address privacy-related concerns, along with the regulatory
   and statutory requirements of some jurisdictions.

   The information that is passed between organizations may include
   authentication state and identity information that can be used for
   many purposes, including making access management decisions.  A
   number of mechanisms support the transmission of this information for
   Web-based scenarios in particular (e.g.  SAML
   [OASIS.saml-profiles-2.0-os]), but there is significant interest in
   the more general application of federated identity to include non-Web
   use cases.  This document enumerates some of these use cases,
   describing how technologies based on the the ABFAB architecture
   [I-D.lear-abfab-arch] and specifications could be used.

2.  Context of Use Cases

   The use cases described in this document are a result of work led by
   Janet, the operator of the United Kingdom's education and research
   network, responding to requirements from its community, and augmented
   by various inputs from the IETF community.

   The ABFAB architecture and specifications enables authentication and
   authorization to occur across organizational boundaries.  For many
   applications, principals need not have pre-instantiated accounts that
   their federated identity maps to before their first visit to that
   application; the application can perform this process on the fly.  In
   cases where such accounts are required for particular applications,
   the pre-provisioning process is out of scope of ABFAB technologies,
   which assumes any such requirements have already been fulfilled.
   Standards-based work of note that would assist with this pre-
   provisioning of accounts includes the standards and specifications
   produced by the IETF SCIM working group.

3.  Use Cases

   This section describes some of the variety of potential use cases
   where technologies based on the ABFAB architecture and specifications
   could help improve the user experience; each includes a brief
   description of how current technologies attempt to solve the use
   cases and how this could improved upon by ABFAB implementations.



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3.1.  Cloud Services

   Cloud computing is emerging as a common way of provisioning
   infrastructure services in an on-demand manner.  These services are
   typically offered as one of three models:

   o  General infrastructure services such as computing power, network,
      storage, and utility ("Infrastructure as a Service", or IaaS);

   o  Software stacks or platforms such as database servers, web
      servers, application runtime environments, etc.  ("Platform as a
      Service", or PaaS);

   o  Common application software such as email, shared storage,
      business applications such as Customer Relationship Management
      (CRM) or scientific applications ("Software as a Service", or
      SaaS).

   In many cases the provisioned cloud infrastructures and applications
   need to be integrated with existing infrastructure of the
   organisation, and it is of course desirable if this could be achieved
   in a way that allows business or scientific workflows to act across
   infrastructure both across the cloud and in the local infrastructure
   in as seamless a manner as possible.

   There are two main areas where federated access fits in cloud
   computing: using federation to help mediate access to cloud based
   application services (e.g. cloud provided email or CRM systems); and
   using federation to help mediate access to the management of cloud
   based infrastructure services.

3.1.1.  Cloud-based Application Services

   Many organizations are seeking to deliver services to their users
   through the use of providers based in the 'cloud'.  This is typically
   motivated by a desire to avoid management and operation of commodity
   services which, through economies of scale and so-forth, can often be
   delivered more efficiently by such providers.

   Many providers already provide web-based access using conventional
   federated authentication mechanisms; for example, outsourced email
   provision where federated access is enabled using 'webmail'
   applications where access is mediated through the use of SAML
   [OASIS.saml-profiles-2.0-os].  This use of federated authentication
   enables organizations that consume cloud services to more efficiently
   orchestrate the delivery of these services to their users, and
   enables Single Sign On to the services for these users.




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   Frequently, however, users will prefer to use desktop applications
   that do not use web (i.e.  HTTP [RFC2616] based) protocols.  For
   example, a desktop email client may use a variety of non-web
   protocols including SMTP [RFC5321], IMAP [RFC3501] and POP [RFC1939].
   Some cloud providers support access to their services using non-web
   protocols, however, the authentication mechanisms used by these
   protocols will typically require that the provider has access to the
   user's credentials - i.e. non federated.  Consequently, the provider
   will require that users' credentials are regularly synchronised from
   the user organisation to the provider, with the obvious overhead this
   imparts on the organisation along with the obvious implications for
   security and privacy; or else be provisioned directly by the provider
   to the user.

   The latter approach of directly provisioning accounts may be
   acceptable in the case where an organisation has relationships with
   only a small number of providers, but may become untenable if an
   organisation obtains services from many providers.  Consequently any
   organisation with a requirement to use non-web protocols would prefer
   to make use of the credentials that they have already provisioned
   their users with, and to utilise federated authentication with non-
   web protocols to obtain access to cloud-based providers.

   ABFAB could help in this context as its specifications would enable
   federated authentication for a variety of non-web protocols, thus
   gaining the benefits of federated authentication without any of the
   drawbacks that are currently experienced.

3.1.2.  Cloud-based Infrastructure Services

   Typical IaaS or PaaS cloud use cases deal with provisioning on-demand
   cloud based infrastructure services that may include infrastructure
   components such as computing and storage resources, network
   infrastructure, and other utilities.  Cloud based virtualised
   applications should ideally operate in the same way as regular non-
   virtualised applications whilst allowing management of the virtual
   computing resources (scaling, migration, reconfiguration) without
   changing the management applications.

   In many cases, moving applications or platforms to the Cloud may
   require their re-designing/re-factoring to support dynamic deployment
   and configuration, including their security and authentication and
   authorisation services.  These will typically today be extensively
   based on manual setup and configuration of such components and
   features as trusted certificates and trust anchors, authorities and
   trusted services (both their location and certificates), attribute
   namespaces, policies, etc.




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   ABFAB could help in this context as a way of moving from the model of
   manually configured authentication and authorisation towards a more
   easily managed system involved federated trust and identity, and will
   be applicable for a wide range of existing features (e.g. connecting
   to a newly provisioned Virtual Machine through ABFAB enabled secure
   shell (SSH) [RFC4251] instead of having to manually manage an
   administrative login to that machine).

3.2.  High Performance Computing

   High-performance computing (HPC) is a discipline that uses
   supercomputers and computer clusters to solve complex computation
   problems; it most commonly associated with scientific research or
   computational science.

   Access to HPC resources, often mediated through technologies such as
   secure shell, is typically managed through the use of user digital
   certificates [RFC5280] or through manually provisioned credentials
   and accounts.  This requires HPC operators to issue certificates or
   accounts to users using a registration process that often duplicates
   identity management processes that already exist within most user
   organizations.  The HPC community would like to utilise federated
   identity to perform both the user registration and authentication
   functions required to use HPC resources, and so reduce costs by
   avoiding this duplication of effort.

   The HPC community also have following additional requirements:

   o  Improved Business Continuity: In the event of operational issues
      at an HPC system at one organisation (for example, a power
      failure), users and jobs could be transparently moved to other HPC
      systems without the overhead of having to manage user credentials
      for multiple organizations;

   o  Establish HPC-as-a-service: Many organizations who have invested
      in HPC systems want to make their systems easily available to
      external customers.  Federated authentication facilitates this by
      enabling these customers to use their existing identity
      management, user credentialing and support processes;

   o  Improve the user experience: Authentication to HPC systems is
      normally performed using user digital certificates, which some
      users find difficult to use.  Federated authentication can provide
      a better user experience by allowing the use of other types of
      credentials, without requiring technical modifications to the HPC
      system to support these.

   ABFAB could help in this context as it could enable federated



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   authentication for the many of the protocols and technologies
   currently in use by HPC providers, such as secure shell.

3.3.  Grid Infrastructure

   Grids are large-scale distributed infrastructures, consisting of many
   loosely coupled, independently managed, and geographically
   distributed resources managed by organisationally independent
   providers.  Users of grids utilise these resources using grid
   middleware that allows them to submit and control computing jobs,
   manipulate datasets, communicate with other users, etc.  These users
   are organised into Virtual Organisations (VOs); each VO represents a
   group of people working collaboratively on a common project.  VOs
   facilitate both the management of its users and the meditation of
   agreements between its users and resource providers.

   Authentication and authorisation within most grids is performed using
   a Public Key Infrastructure, requiring each user to have an X.509
   public-key certificate [RFC5280].  Authentication is performed
   through ownership of a particular certificate, while authorisation
   decisions are made based on the user's identity (derived from their
   X.509 certificate), membership of a particular VO, or additional
   information assigned to a user by a VO.  While efficient and
   scalable, this approach has been found wanting in terms of usability
   - many users find certificates difficult to manage, for various
   reasons.

   One approach to ameliorating this issue, adopted to some extent by
   some grid communities already, is to abstract away direct access to
   certificates from users, instead using alternative authentication
   mechanisms and then converting the credential provided by these into
   standard grid certificates.  Some implementations of this idea use
   existing federated authentication techniques.  However, current
   implementations of this approach suffer from a number of problems,
   not the least of which is the inability to use the federated
   credentials used to authenticate to a credential-conversion portal to
   also directly authenticate to non-web resources such as secure shell
   daemons.

   The ability to use federated authentication directly through ABFAB,
   without the use of a credential conversion service, would allow users
   to authenticate to a grid and its associated services, allowing them
   to directly launch and control computing jobs, all without having to
   manage, or even see, an X.509 public-key certificate at any point in
   the process.  Authorisation within the grid would still be performed
   using VO membership asserted issued by the user's identity provider
   through the federated transport.




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3.4.  Databases and Directories

   Databases (e.g.  MySQL, PostgreSQL, Oracle, etc.) and directory
   technologies (e.g.  OpenLDAP, Microsoft Active Directory, Novell
   eDirectory, etc.) are very commonly used within many organsiations
   for a variety of purposes.  This can include core administrative
   functions, such as hosting identity information for its users, as
   well as business functions (e.g. student records systems at
   educational organizations).

   Access to such database and directory systems is usually provided for
   internal users only, however, users external to the organizations
   sometimes require access to these systems directly: for example,
   external examiners in educational organizations requiring access to
   student records systems, members of cross-organisational project
   teams who store information in a particular organisation's systems,
   external auditors, etc.

   Credentials for users both internal or external to the organisation
   that allow access these databases and directories are usually
   provisioned manually within an organisation, either using Identity
   Management technologies or through more manual processes.  For the
   internal users, this situation is fine - this is one of the mainstays
   of Identity Management.  However, for external users who require
   access, this represents more of a problem for organisational
   processes.  The organisation either has to add these external users
   to its internal Identity Management systems, or else provision these
   credentials directly within the database/directory systems and
   continue to manage them, including appropriate access controls
   associated with each credential, for the lifetime of that credential.

   Federated authentication to databases or directories, via ABFAB
   technologies, would improve upon this situation as it would remove
   the need to provision and de-provision credentials to access these
   systems.  Organisations may still wish to manually manage access
   control of federated identities; however, even this could be provided
   through federated means, if the trust relationship between
   organizations was strong enough for the organisation providing the
   service to rely upon it for this purpose.

3.5.  Media Streaming

   Media streaming services (audio or audio/video) are often provided
   publicly to anonymous users, but authentication is important for a
   protected subset of streams where rights management and access
   control must be applied.

   Streams can be delivered via protocols such as RTSP [RFC3226] / RTP



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   [RFC3550] which already include authentication, or can be published
   in an encrypted form with keys only being distributed to trusted
   users.  Federated authentication is applicable to both of these
   cases.

   Alternative mechanisms to managing access exist; for example, an
   approach where a unique stream URI is minted for each user.  However,
   this relies on preserving the secrecy of the stream URI, and also
   requires a communication channel between the web page used for
   authentication and the streaming service itself.  Federated
   authentication would be a better fit for this kind of access control.
   Thus, AFAB technologies that allow federated authentication directly
   within (inherently non-web) media streaming protocols would represent
   an enhancement to this area.

3.6.  Printing

   A visitor from one organisation to the premises of another often
   requires the use of print services.  Their home organisation may of
   course offer printing, but the output could be a long way away so the
   home service is not useful.  The user will typically want to print
   from within a desktop or mobile application.

   Where this service is currently offered it would usually be achieved
   through the use of 'open' printers (i.e. printers that allow
   anonymous print requests), where printer availability is advertised
   through the use of Bonjour or other similar protocols.  If the
   organisation requires authenticated print requests (usually for
   accounting purposes), the the visitor would usually have to be given
   credentials that allow this, often supplemented with pay-as-you-go
   style payment systems.

   Adding federated authentication to IPP [RFC2911] (and other relevant
   protocols) would enable this kind of remote printing service without
   the administrative overhead of credentialing these visitors (who, of
   course, may well one time visitors to the organisation).  This would
   be immediately applicable to higher education, where this use case is
   increasingly important thanks to the success of federated network
   authentication systems such as eduroam but could also be used in
   other contexts such as commercial print kiosks, or in large,
   heterogeneous organizations.

3.7.  Accessing Applications from Devices on a Telecoms Infrastructure

   Telecom operators typically have the following properties:

   o  A large collection of registered users, many of whom may have
      identities registered to a fairly high level of assurance (often



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      for payment purposes).  However, not all users will have this
      property - for example, non-contract customers on mobile telecoms
      infrastructures in countries with low levels of identity
      registration requirements.

   o  An existing network infrastructure capable of authenticating a
      device (e.g. a cellphone or an ADSL router), and by inference, its
      owner.

   o  A large collection of applications (both web-based and non web-
      based) that its users wish to access using their device.  These
      applications could be hosted by the telecoms operator directly, or
      could be any application or system on the internet - for example,
      network messaging services, VoIP, email, etc.

   At present, authentication to these applications will be typically
   configured manually by the user on the device (or on a different
   device connected to that device) but inputting their (usually pre-
   provisioned out-of-band) credentials for that application - one per
   application.

   The use of ABFAB technologies in this case, via a mechanism dubbed
   "federated cross-layer access" (see [I-D.wei-abfab-fcla]) would
   enhance the user experience of using these applications through
   devices greatly.  Federated cross-layer access would make use of the
   initial mutual authentication between device and network to enable
   subsequent authentication and authorisation to happen in a seamless
   manner for the user of that device authenticating to applications.

3.8.  Enhanced Security Services for S/MIME

   There are many situations where organizations want to protect
   information with robust access control, either for implementation of
   intellectual property right protections, enforcement of contractual
   confidentiality agreements or because of legal regulations.  The
   Enhanced Security Services (ESS) for S/MIME defines an access control
   mechanism which is enforced by the recipient's client after
   decryption of the message (see [I-D.freeman-plasma-requirements]).
   The data model used makes use of Policy decision points (PDP) which
   make the policy decisions, policy enforcement points (PEP) which make
   decision requests to the PDP, and policy information points (PIP)
   which issue attributes about subjects.  The decisions themselves are
   based on the policies and on the subject attributes.

   The use of ABFAB technologies in this case would enable both the
   front or back end attribute exchange required to provide subject
   attributes.  When the PEP contacts the PDP, it would initiate an
   ABFAB authentication in order to authenticate to the PDP and allow it



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   to obtain these required subject attributes.  Once authenticated, the
   PDP would return a token to the subject PEP which can be used for
   subsequent authentications to the PDP.

3.9.  Smart Objects

   Many smart device deployments involve multiple organizations that do
   not directly share security infrastructure.  For example, in smart
   power deployments, devices including appliances and infrastructure
   such as electric car chargers will wish to connect to an energy
   management system.  The energy management system is provided by a
   utility company in some deployments.  The utility company may wish to
   grant access only to authorized devices; for example, a consortium of
   utility companies and device manufacturers may certify devices to
   connect to power networks.

   In another example, consumer devices may be used to access cloud
   services.  For example, a camera could be bound to a photo processing
   site.  Authentication and authorization for uploading pictures or
   ordering prints is required.  Sensors could be used to provide data
   to services run by organizations other than the sensor manufacturer.
   Authorization and authentication can become very tricky when sensors
   have no user interface.  Cellular devices may want to access services
   provided by a third party regardless of whether the cellular network
   or wi-fi is used.  This becomes difficult when authorization and
   billing is coordinated by the cellular provider.

   The use of ABFAB technologies in this case would provide
   authentication between one entity, such as a smart device, and its
   identity provider.  Only two parties are involved in this exchange;
   this means that the smart device need not participate in any
   complicated public-key infrastructure even if it is authenticating
   against many cloud services.  Instead, the device can delegate the
   process of authenticating the service and even deciding whether the
   device should be permitted to access the service to the identity
   provider.  This has several advantages.  A wide variety of revenue
   sharing models are enabled.  Because device authentication is only
   with a single identity provider, phishing of device credentials can
   be avoided.  Authorization and decisions about what personal
   information to release are made by the identity provider.  The device
   owner can use a rich interface such as a website to configure
   authorization and privacy policy even if the device has no user
   interface.  This model works well with pre-provisioning of device
   credentials.







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4.  Contributors

   The following individuals made important contributions to the text of
   this document: Tim Bannister (Manchester University), Simon Cooper
   (Janet), Josh Howlett (Janet), and Mark Tysom (Janet).

5.  Acknowledgements

   These use-cases have been developed and documented using significant
   input from Jens Jensen (STFC Rutherford Appleton Laboratory), Daniel
   Kouril (CESNET), Michal Prochazka (CESNET), Ian Stewart (University
   of Edinburgh), Stephen Booth (Edinburgh Parallel Computing Centre),
   Eefje van der Harst (SURFnet), Joost van Dijk (SURFnet), Robin
   Breathe (Oxford Brookes University), Yinxing Wei (ZTE Corporation),
   Trevor Freeman (Microsoft Corp.), Sam Hartman (Painless Security,
   LLC), and Yuri Demchenko (University of Amsterdam).

6.  Security Considerations

   This document contains only use cases and defines no protocol
   operations for ABFAB.  Security considerations for the ABFAB
   architecture are documented in the ABFAB architecture specification,
   and security considerations for ABFAB technologies and protocols that
   are discussed in these use cases are documented in the corresponding
   protocol specifications.

7.  IANA Considerations

   This document does not require actions by IANA.

8.  References

8.1.  Normative References

   [I-D.lear-abfab-arch]              Howlett, J., Hartman, S.,
                                      Tschofenig, H., and E. Lear,
                                      "Application Bridging for
                                      Federated Access Beyond Web
                                      (ABFAB) Architecture",
                                      draft-lear-abfab-arch-02 (work in
                                      progress), March 2011.

8.2.  Informative References

   [RFC1939]                          Myers, J. and M. Rose, "Post
                                      Office Protocol - Version 3",
                                      STD 53, RFC 1939, May 1996.




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   [RFC2616]                          Fielding, R., Gettys, J., Mogul,
                                      J., Frystyk, H., Masinter, L.,
                                      Leach, P., and T. Berners-Lee,
                                      "Hypertext Transfer Protocol --
                                      HTTP/1.1", RFC 2616, June 1999.

   [RFC2911]                          Hastings, T., Herriot, R., deBry,
                                      R., Isaacson, S., and P. Powell,
                                      "Internet Printing Protocol/1.1:
                                      Model and Semantics", RFC 2911,
                                      September 2000.

   [RFC3226]                          Gudmundsson, O., "DNSSEC and IPv6
                                      A6 aware server/resolver message
                                      size requirements", RFC 3226,
                                      December 2001.

   [RFC3501]                          Crispin, M., "INTERNET MESSAGE
                                      ACCESS PROTOCOL - VERSION 4rev1",
                                      RFC 3501, March 2003.

   [RFC3550]                          Schulzrinne, H., Casner, S.,
                                      Frederick, R., and V. Jacobson,
                                      "RTP: A Transport Protocol for
                                      Real-Time Applications", STD 64,
                                      RFC 3550, July 2003.

   [RFC4251]                          Ylonen, T. and C. Lonvick, "The
                                      Secure Shell (SSH) Protocol
                                      Architecture", RFC 4251,
                                      January 2006.

   [RFC5280]                          Cooper, D., Santesson, S.,
                                      Farrell, S., Boeyen, S., Housley,
                                      R., and W. Polk, "Internet X.509
                                      Public Key Infrastructure
                                      Certificate and Certificate
                                      Revocation List (CRL) Profile",
                                      RFC 5280, May 2008.

   [RFC5321]                          Klensin, J., "Simple Mail Transfer
                                      Protocol", RFC 5321, October 2008.

   [OASIS.saml-profiles-2.0-os]       Hughes, J., Cantor, S., Hodges,
                                      J., Hirsch, F., Mishra, P.,
                                      Philpott, R., and E. Maler,
                                      "Profiles for the OASIS Security
                                      Assertion Markup Language (SAML)



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Internet-Draft               ABFAB Use Cases              September 2012


                                      V2.0", OASIS Standard OASIS.saml-
                                      profiles-2.0-os, March 2005.

   [I-D.wei-abfab-fcla]               Wei, Y., "Federated Cross-Layer
                                      Access", draft-wei-abfab-fcla-02
                                      (work in progress), March 2012.

   [I-D.freeman-plasma-requirements]  Freeman, T., Schaad, J., and P.
                                      Patterson, "Requirements for
                                      Message Access Control", draft-
                                      freeman-plasma-requirements-03
                                      (work in progress), August 2012.

Author's Address

   Dr. Rhys Smith (editor)
   Cardiff University
   39-41 Park Place
   Cardiff  CF10 3BB
   United Kingdom

   Phone: +44 29 2087 0126
   EMail: smith@cardiff.ac.uk




























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