Report from the Smart Object Security Workshop

Independent Submission                                         J. Gilger
Request for Comments: 7397                                 H. Tschofenig
Category: Informational                                    December 2014
ISSN: 2070-1721


             Report from the Smart Object Security Workshop

Abstract

   This document provides a summary of a workshop on 'Smart Object
   Security' that took place in Paris on March 23, 2012.  The main goal
   of the workshop was to allow participants to share their thoughts
   about the ability to utilize existing and widely deployed security
   mechanisms for smart objects.

   This report summarizes the discussions and lists the conclusions and
   recommendations to the Internet Engineering Task Force (IETF)
   community.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7397.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   to this document.

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................3
   3. Workshop Structure ..............................................3
      3.1. Requirements and Use Cases .................................4
      3.2. Implementation Experience ..................................7
      3.3. Authorization .............................................10
      3.4. Provisioning of Credentials ...............................12
   4. Summary ........................................................14
   5. Security Considerations ........................................15
   6. References .....................................................16
      6.1. Normative References ......................................16
      6.2. Informative References ....................................16
   Appendix A. Program Committee .....................................18
   Appendix B. Published Workshop Material ...........................18
   Appendix C. Accepted Position Papers ..............................18
   Appendix D. Workshop Participants .................................21
   Acknowledgements ..................................................22
   Authors' Addresses ................................................23

1.  Introduction

   In early 2011, the Internet Architecture Board (IAB) solicited
   position statements for a workshop on 'Interconnecting Smart Objects
   with the Internet', aiming to get feedback from the wider Internet
   community on their experience with deploying IETF protocols in
   constrained environments.  The workshop took place in Prague on March
   25, 2011.  During the workshop, a range of topics were discussed,
   including architecture, routing, energy efficiency, and security.
   RFC 6574 [RFC6574] summarizes the discussion and suggests several
   next steps.

   During the months following the workshop, new IETF initiatives were
   started, such as the Light-Weight Implementation Guidance (LWIG)
   working group, and hackathons were organized at IETF 80 and IETF 81
   to better facilitate the exchange of ideas.

   Contributions regarding security from the IETF Constrained RESTful
   Environments (CoRE) working group and the IETF Transport Layer
   Security (TLS) working group made it clear that further discussions
   on security were necessary and that those would have to incorporate
   implementation and deployment experience as well as a shared
   understanding of how various building blocks fit into a larger
   architecture.

   The workshop on 'Smart Object Security' was organized to bring
   together various disconnected discussions about smart object
   security happening in different IETF working groups and industry
   fora.  It was a one-day workshop held prior to the IETF 83 in Paris
   on March 23, 2012.

   The workshop organizers were particularly interested in getting input
   on the following topics, as outlined in the call for position papers:

   o  What techniques for issuing credentials have been deployed?

   o  What extensions are useful to make existing security protocols
      more suitable for smart objects?

   o  What type of credentials are frequently used?

   o  What experience has been gained when implementing and deploying
      application-layer, transport-layer, network-layer, and link-layer
      security mechanisms (or a mixture of all of them)?

   o  How can "clever" implementations make security protocols a better
      fit for constrained devices?

   o  Are there lessons we can learn from existing deployments?

   This document lists some of the recurring discussion topics at the
   workshop.  It also offers recommendations from the workshop
   participants.

   Note that this document is a report on the proceedings of the
   workshop.  The views and positions documented in this report are
   those of the workshop participants and do not necessarily reflect the
   views of the authors or the Internet Architecture Board (IAB).

2.  Terminology

   This document uses security terminology from [RFC4949] and terms
   related to smart objects from [RFC6574].

3.  Workshop Structure

   With 35 accepted position papers, there was a wealth of topics to
   talk about during the one-day workshop.  The program committee
   decided to divide the discussion into four topic areas ("Requirements
   and Use Cases", "Implementation Experience", "Authorization", and
   "Providing Credentials"), with two or three invited talks per slot to
   get a discussion started.  This section will summarize the points
   raised by the invited speakers as well as the essence of the ensuing
   discussions.

3.1.  Requirements and Use Cases

   To design a security solution, an initial starting point is to
   understand the communication relationships, the constraints, and the
   security threats.  The typical IETF Security Considerations section
   describes security threats, security requirements, and security
   solutions at the level of a single protocol or a single document.  To
   offer a meaningful solution for a smart object deployment, it is,
   however, necessary to go beyond this limited view to the analysis of
   the larger ecosystem.  The security analysis documented in [RFC3552]
   and in [RFC4101] still provides valuable guidance.

   Typical questions that arise are:

   1.  Who are the involved actors?

       Some usage scenarios look very simple at first but then, after a
       longer investigation, turn out to be quite complex.  The smart
       meter deployment, for example, certainly belongs to one of the
       more complex deployments due to the history of the energy sector
       (see [RFC6272]).

   2.  Who provisions credentials?

       Credentials may, for example, be provisioned by the end user, the
       hardware manufacturer, an application service provider, or other
       parties.  With security provided at multiple layers, credentials
       from multiple parties may need to be provisioned.

   3.  What constraints are imposed on the design?

       For example, a constraint can be the need to interwork with
       existing infrastructure.  From an architectural point of view, an
       important question is whether security is terminated at the
       border router (or proxy server) at the customer's premise or if
       end-to-end security to servers in the Internet is required.  A
       more detailed discussion can be found at [SMART-OBJECT].

   4.  What type of authorization is required by the identified actors?

       This may, for example, be authorization to get access to the
       network or authorization at the application layer.  Authorization
       decisions may be binary or may consist of complex, role-based
       access control policies.

   5.  What tasks are expected by the customer who deploys the solution?

       An end customer may, for example, be expected to enter short PIN
       codes to pair devices, need to update the firmware, or need to
       connect to an appliance via a web browser to make more
       sophisticated configuration settings.  The familiarity of end
       users with Internet-based devices certainly increases constantly,
       but user-interface challenges contribute to a large number of
       security weaknesses of the Internet and therefore have to be
       taken into account.

   To illustrate the differences, consider a mass-market deployment for
   end customers in comparison to a deployment that is targeting
   enterprise customers.  In the latter case, enterprise system
   administrators are likely to utilize different management systems to
   provision security and other system-relevant parameters.

   Paul Chilton illustrated the security and usability requirements in a
   typical end-user scenario for small-scale smart lighting systems
   [PaulChilton].  These systems present a substantial challenge for
   providing usable and secure communication because they are supposed
   to be cheap and very easy to set up, ideally as easy as their "dumb"
   predecessors.  The example of IP-enabled light bulbs shows that the
   more constrained devices are, the more difficult it is to get
   security right.  For this reason, and the required usability, light
   bulbs might just be the perfect example for examining the viability
   of security solutions.

   Rudolf van der Berg focused on large-scale deployments of smart
   objects, such as eBook readers, smart meters, and automobiles.  The
   use of mobile cellular networks is attractive because they are
   networks with adequate coverage and capacity on a global scale.  In
   order to make use of mobile networks, you need to make use of
   authentication based on Subscriber Identity Modules (SIMs).  However,
   at this moment, the SIM is controlled by the network operator.  These
   companies could also use EAP-SIM (Extensible Authentication Protocol
   SIM) [RFC4186] authentication in, for example, wireless LANs.

   The end-user interaction may differ depending on the credentials
   being used: for a light bulb deployed in the user's home, it is
   expected that the user somehow configures devices so that only, for
   example, family members can turn them on and off.  Smart objects that
   are equipped with SIM-based credential infrastructure do not require
   credential management by the end user since credential management by
   the operator can be assumed.  Switching cellular operators may,
   however, pose challenges for these devices.

   Furthermore, we have a technology that will be both deployed by end
   users and large enterprise customers.  While the protocol building
   blocks may be the same, there is certainly a big difference between
   deployments for large-scale industrial applications and deployments
   for regular end users in terms of the architecture.  Between these
   two, the security requirements differ significantly, as do the
   threats.  It is difficult, if not impossible, to develop a single
   security architecture that fulfills the needs of all users while at
   the same time meeting the constraints of all kinds of smart objects.

   In the consumer market, security should not incur any overhead during
   installation.  If an end user has to invest more time or effort to
   secure a smart object network, he or she will likely not do it.
   Consumer products will often be retrofitted into the existing
   infrastructure, bought, and installed by consumers themselves.  This
   means that devices will have to come pre-installed to some extent and
   will most likely interoperate only with the infrastructure provided
   by the vendor, i.e., the devices will be able to connect to the
   Internet but will only interoperate with the servers provided by the
   vendor selling the device.

   Closed systems (one bulb, one switch) typically work out of the box,
   as they have been extensively tested and often come with factory-
   configured security credentials.  Problems do arise when additional
   devices are added or when these closed systems get connected to the
   Internet.  It is still very common to ship devices with default
   passwords.  It is, however, not acceptable that a device is in a
   vulnerable, but Internet-connected, state before it has been
   correctly configured by a consumer.  It is easy to conceive that many
   consumers do not configure their devices properly and may therefore
   make it easy for an adversary to take control of the device by, for
   example, using the default password or outdated firmware.

   Once security threats for a specific deployment scenario have been
   identified, an assessment takes place to decide what security
   requirements can be identified and what security properties are
   desirable for the solution.  As part of this process, a conscious
   decision needs to take place about which countermeasures will be used
   to mitigate certain threats.  For some security threats, the
   assessment may also lead to the conclusion that the threat is
   considered out-of-scope and, therefore, no technical protection is
   applied.  Different businesses are likely to come to different
   conclusions about the priorities for protection and what security
   requirements will be derived.

   Which security threats are worthwhile to protect against is certainly
   in the eye of the beholder and remains an entertaining discussion
   even among security specialists.  For some of the workshop
   participants, the security threats against a smart lighting system
   were considered relatively minor compared to other smart home
   appliances.  Clearly, the threats depend on the specific application
   domain, but there is a certain danger that deployments of vulnerable
   smart objects will increase.  As the systems evolve and become more
   pervasive, additional security features may be required and may be
   difficult to incorporate into the already installed base,
   particularly if smart objects have no software update mechanism
   incorporated in their initial design.  Smart objects that require
   human interaction to perform software updates will likely be
   problematic in the future.  This is particularly true for devices
   that are expected to have service schedules of five to twenty-five
   years.  Experience shows that security breaches that are considered
   pranks usually evolve very rapidly to become destructive attacks.

   Apart from the security requirements of individual households and
   users, it is also important to look at the implications of
   vulnerabilities in large-scale smart object deployments, for example,
   in smart meters and the power grid.

   Finally, there is the usual wealth of other requirements that need to
   be taken into account, such as ability for remote configuration and
   software updates, the ability to deal with transfer of ownership of a
   device, avoidance of operator or vendor lock-in, crypto agility,
   minimal production, license and IPR costs, etc.

3.2.  Implementation Experience

   The second slot of the workshop was dedicated to reports from first-
   hand implementation experience.  Various participants had provided
   position papers exploring different security protocols and
   cryptographic primitives.  There were three invited talks that
   covered tiny implementations of the Constrained Application Protocol
   (CoAP) protected by Datagram Transport Layer Security (DTLS), a TLS
   implementation using raw public keys, and general experience with
   implementing public key cryptography on smart object devices.

   All three presenters demonstrated that implementations of IETF
   security protocols on various constraint devices are feasible.  This
   was confirmed by other workshop participants as well.  The overall
   code size and performance of finished implementations will depend on
   the chosen feature set.  It is fairly obvious that more features
   translate to a more complex outcome.  Luckily, IETF security
   protocols in general (and TLS/DTLS is no exception) can be customized
   in a variety of ways to fit a specific deployment environment.  As
   such, an engineer will have to decide which features are important
   for a given deployment scenario and what trade-offs can be made.
   There was also the belief that IETF security protocols offer useful
   customization features (such as different ciphersuites in TLS/DTLS)
   to select the desired combination of algorithms and cryptographic
   primitives.  The need to optimize available security protocols
   further or to even develop new cryptographic primitives for smart
   objects was questioned and not seen as worthwhile by many
   participants.

   The three common constraints for security implementations on smart
   objects are code size, energy consumption, and bandwidth.  The
   importance of tailoring a solution to one of these constraints
   depends on the specific deployment environment.  It might be
   difficult to develop a solution that addresses all constraints at the
   same time.  For example, minimizing memory use may lead to increased
   communication overhead.

   Waiting for the next generation of hardware typically does not
   magically lift the constraints faced today.  The workshop
   participants again reinforced the message that was made at the
   earlier smart object workshop [RFC6574] regarding future developments
   in the smart object space:

      While there are constantly improvements being made, Moore's law
      tends to be less effective in the embedded system space than in
      personal computing devices: gains made available by increases in
      transistor count and density are more likely to be invested in
      reductions of cost and power requirements than into continual
      increases in computing power.

   The above statement is applicable to smart object designs in general,
   not only for security.  Thus, it is expected that designers will
   continue having to deal with various constraints of smart objects in
   the future.  A short description of the different classes of smart
   objects can be found in [RFC7228], which also provides security-
   related guidance.  The workshop participants noted that making
   security protocols suitable for smart objects must not water down
   their effectiveness.  Security functionality will demand some portion
   of the overall code size.  It will have an impact on the performance
   of communication interactions, lead to higher energy consumption, and
   certainly make the entire product more complex.  Still, omitting
   security functionality because of various constraints is not an
   option.  The experience with implementing available security
   protocols was encouraging even though the need to make various
   architectural design decisions for selecting the right set of
   protocols and protocol extensions that everyone must agree on was
   pointed out.  Sometimes, the leading constraint is energy
   consumption, and in other cases, it is main memory, CPU performance,
   or bandwidth.  In any case, for an optimization, it is important to
   look at the entire system rather than a single protocol or even a
   specific algorithm.

   Equally important to the code size of the protocols being used in a
   deployed product are various other design decisions, such as the
   communication model, the number of communication partners, the
   interoperability requirements, and the threats that are being dealt
   with.  Mohit Sethi noted that even the execution time for relatively
   expensive operations like asymmetric signature generation and
   verification are within acceptable limits for very constrained
   devices, like an Arduino UNO.  In either case, public key
   cryptography will likely only be used for the initial communication
   setup to establish symmetric session keys.  Perhaps surprisingly, the
   energy cost of transmitting data wirelessly dwarfs even expensive
   computations like public key cryptography.  Since wireless reception
   is actually the most power-consuming task on a smart object,
   protocols have to be designed accordingly.

   The workshop participants shared the view that the complexity of
   security protocols is a result of desired features.  Redesigning a
   protocol with the same set of features will, quite likely, lead to a
   similar outcome in terms of code size, memory consumption, and
   performance.  It was, however, also acknowledged that the security
   properties offered by DTLS/TLS/IKEv2-IPsec may not be needed for all
   deployment environments.  DTLS, for example, offers an authentication
   and key exchange framework combined with channel security offering
   data-origin authentication, integrity protection, and (optionally)
   confidentiality protection.

   The biggest optimization in terms of code size can be gained when
   looking at the complete protocol stack, rather than only
   cryptographic algorithms.  This also includes software update
   mechanisms and configuration mechanisms, all of which have to work
   together.  What may not have been investigated enough is the
   potential of performing cross-layer and cross-protocol optimization.
   We also need to think about how many protocols for security setup we
   want to have.  Due to the desire to standardize generic building
   blocks, the ability to optimize for specific deployment environments
   has been reduced.

   Finally, it was noted that scalability of security protocols does not
   imply usability.  This means that while smart object technology might
   currently be developed in large-scale industrial environments, it
   should be equally usable for consumers who want to equip their home
   with just a few light bulbs.

   For details about the investigated protocol implementations, please
   consult the position papers, such as the ones by Bergmann et al.,
   Perelman et al., Tschofenig, and Raza et al. (see Appendix C).

3.3.  Authorization

   The discussion slot on authorization was meant to provide an idea of
   what kind of authorization decisions are common in smart object
   networks.  Authorization is defined as an "approval that is granted
   to a system entity to access a system resource" [RFC4949].

   Authorization requires a view on the entire smart object lifecycle to
   determine when and how a device was added to a specific environment,
   what permissions have been granted for this device, and how users are
   allowed to interact with it.  On a high level, there are two types of
   authorization schemes.  First, there are those systems that utilize
   an authenticated identifier and match it against an access control
   list.  Second, there are trait-based authorization mechanisms that
   separate the authenticated identifier from the authorization rights
   and utilize roles and other attributes to determine whether to grant
   or deny access to a protected resource.

   Richard Barnes looked at earlier communication security work and
   argued that the model that dominates the web today will not be enough
   for the smart object environment.  Simply identifying users by their
   credentials and servers via certificates is not something that
   translates well to smart object networks because it binds all the
   capabilities to the credentials.  The evolution in access control is
   moving in the direction of granting third parties certain
   capabilities, with OAuth [RFC6749] being an example of a currently
   deployed technology.  Access to a resource using OAuth can be done
   purely based on the capabilities rather than on the authenticated
   identifier.

   At the time of the workshop, OAuth was very much focused on
   HTTP-based protocols with early efforts to integrate OAuth into the
   Simple Authentication and Security Layer (SASL) and the Generic
   Security Service Application Program Interface (GSS-API)
   [SASL-OAUTH].  Further investigations need to be done to determine
   the suitability of OAuth as a protocol for the smart object
   environment.

   Richard believed that it is important to separate authentication from
   authorization right from the beginning and to consider how users are
   supposed to interact with these devices to introduce them into their
   specific usage environment (and to provision them with credentials)
   and to manage access from different parties.

   The relationship between the policy enforcement point and the policy
   decision point plays an important role regarding the standardization
   needs and the type of information that needs to be conveyed between
   these two entities.

   For example, in an Authentication, Authorization, and Accounting
   (AAA) context, the authorization decision happens at the AAA server
   (after the user requesting access to a network or some application-
   level services had been authenticated).  Then, the decision about
   granting access (or rejecting it) is communicated from the AAA server
   to the AAA client at the end of the network access authentication
   procedure.  The AAA client then typically enforces the authorization
   decision over the lifetime of the granted user session.  The dynamic
   authorization extension [RFC5176] to the RADIUS protocol, for
   example, also allows the RADIUS server to make dynamic changes to a
   previously granted user session.  This includes support for
   disconnecting users and changing authorizations applicable to a user
   session.

   The authorization decisions can range from 'only devices with
   passwords can use the network' to very detailed application-specific
   authorization policies.  The decisions are likely to be more
   sophisticated in those use cases where ownership of devices may be
   transferred from one person to another one, group membership concepts
   may be needed, access rights may be revocable, and fine-grained
   access rights have to be used.  The authorization decisions may also
   take environmental factors into account, such as proximity of devices
   to each other, physical location of the device asking access, or the
   level of authentication.  With the configuration of authorization
   policies, questions arise regarding who will create them and where
   these policies are stored.  This immediately raises questions about
   how devices are identified and who is allowed to create these
   policies.

   Since smart objects may be limited in terms of code size, persistent
   storage, and Internet connectivity, established authorization schemes
   may not be well suited for such devices.  Obviously, delegating every
   authorization decision to another node in the network incurs a
   certain network overhead, while storing sophisticated access control
   policies directly on the smart object might be prohibitive because of
   the size of such a ruleset.  Jan Janak presented one approach to
   distribute access control policies to smart objects within a single
   administrative domain.

   In those cases where access control decisions are bound to the
   identifiers of devices and humans need to either create or verify
   these access control policies, the choice of identifier matters for
   readability and accessibility purposes.

   A single mechanism will likely not help with solving the wide range
   of authorization tasks.  From the discussions, it was not clear
   whether there is a need for new authorization mechanisms or whether
   existing mechanisms can be reused.  Examples of available protocols
   with built-in authorization mechanisms are Kerberos, OAuth, EAP/AAA,
   attribute certificates, etc.  In many cases, it is even conceivable
   that the authorization decisions are internal to the system and that
   there is no need to standardize any additional authorization
   mechanisms or protocols at all.  In fact, many of the authentication
   and key exchange protocols have authorization mechanisms built in.

3.4.  Provisioning of Credentials

   When a smart object is to be introduced into an environment, like a
   home or an enterprise network, it usually has to be provisioned with
   some credentials first.  The credentials that are configured at the
   smart object and at some entity in the network are often an implicit
   authorization to access the network or some other resource.  The
   provisioned information at the smart object will include some
   identifier of the smart object, keying material, and other
   configuration information (e.g., specific servers it has to interact
   with).

   Some devices will be pre-configured with default security codes or
   passwords, or will have per-device or per-user credentials
   pre-configured, when they are bought or when they arrive at the
   customer.

   There is a limited set of solutions available (based on the available
   interface support).  The solutions for imprinting vary between the
   enterprise and the consumer household scenarios.  For large-scale
   deployments, the time needed to pair two objects further excludes
   other schemes that rely on manual steps.

   Johannes Gilger dealt with the very basic ideas behind pairing
   schemes, including the kinds of out-of-band channels that could be
   employed and their limitations.  Imprinting and pairing protocols
   usually establish a security association between two equal devices,
   such as Bluetooth-equipped cell phones.  To deal with man-in-the-
   middle attacks during this phase, various forms of additional
   verification checks exist.  For example, devices with a display allow
   numeric values to be shown on each device and let the user verify
   whether they match.  For other devices that have a keypad, a PIN may
   need to be entered by the user.  Where and how a smart object is to
   be paired with other devices in the network can differ substantially
   from the specific use cases and the hardware capabilities of devices.
   Note that pairing is not necessarily something that is only done once
   during the lifetime of a device.  Is group pairing something to be
   looked at?  Or can any group key establishment be reduced to pairwise
   pairing with a central master device?

   Cullen Jennings presented a model for smart objects based on a
   deployment used for IP phones.  The idea was that the smart object
   "phones home", i.e., contacts a server offered by the manufacturer,
   when it is first switched on.  This initial interaction can then be
   used for managing the device and provisioning keying material for
   further use.  Proof of ownership could be done by identifying the
   user who purchased the device.  This is an approach that is
   increasingly being done today.  Another option is some kind of secret
   information enclosed in the packaging.

   For interface-constrained devices, the solution of using (semi)-
   public information in combination with an online manufacturer during
   imprinting seems like a possible solution.  This solution approach
   created a lot of discussion among the participants, as it assumes an
   Internet connection and means that the manufacturer effectively knows
   about the trust relationships of all the devices it sells.

   A few questions did arise with such a model: Will there be third
   parties that have a business interest in providing something like key
   distribution and key escrow over the lifetime of a smart object?  For
   constrained devices, will it always be possible to fall back to the
   existing security associations between device and manufacturer to
   create new associations?  Obviously, we do not want the lifetime of a
   smart object limited by the manufacturer product support lifespan.
   What happens if a manufacturer goes bankrupt, changes its business
   scope, or gets bought by another company?  Will end customers not be
   able to use their smart objects anymore in such a case, or will they
   lose the ability to resell their devices because the ownership can no
   longer be transferred?

   One important design decision is that the compromise of the
   manufacturer must not have any impact on the smart objects, which
   have already been imprinted to their new owners.  Furthermore, the
   question arises of how to transfer ownership, e.g., when reselling a
   device.  While this may not be a requirement for all devices, there
   will likely be classes of large or expensive devices where support
   for transferring the ownership is an absolute necessity.

   Industrial users are comfortable when they have to rely on the
   manufacturer during the imprinting phase, but they want to be in
   exclusive control over their devices afterwards.

   There are many classes of devices where we could assume online
   connectivity to be present; otherwise, these devices would not make
   sense in the first place.  But, there are also other devices that
   need to be imprinted completely offline.

   Is it important to worry about security vulnerabilities, such as
   man-in-the-middle attacks, during the very short imprinting phase?
   Is it realistic that an adversary is in close proximity to mount an
   attack?  Especially for devices with limited capabilities, such as
   light bulbs, the concerns seemed rather small.

   What happens if such a device is not enrolled by the customer but
   still connected in a "naked" state?  How does this impact security,
   and is it possible for an attacker to perform a "drive-by" enrollment
   procedure of many devices?  How should a device behave in this
   situation?  The safest option (for the user at least) would be to not
   allow the device to work with full functionality if it has not been
   enrolled.  This concern is particularly applicable for cases where
   smart objects are sold with default passwords or passwords using
   semi-public information; an example is Raspberry Pi computers with
   Linux images that use a default password [RaspberryPi].

4.  Summary

   Designing for a smart object environment is about making an
   optimization decision that needs to take technical aspects, usage
   scenarios, security threats, and business models into account.  Some
   design constraints may be considered fixed while others are flexible.
   Compromises will need to be made, but they should not be made at the
   expense of security functionality.

   Designing a software update mechanism into the system is crucial to
   ensure that functionality can be enhanced and vulnerabilities can be
   fixed.  Also, security threats are perceived differently over time.
   For example, many people considered pervasive monitoring less
   important prior to the Snowden revelations.

   New research and standardization on cryptographic algorithms (like
   encryption algorithms, hash functions, keyed message digests, and
   public key crypto systems) that are tailored to smart object
   environments was not seen as worthwhile by the participants.  A huge
   range of algorithms already exist, and standardized authentication
   and key exchange protocols can be customized to use almost any
   selection of algorithms available today.

   The integration of various building blocks into a complete system was
   considered important, and this document highlights a number of those
   areas in Section 3.  Searching for a single, universally applicable
   smart object security architecture was seen as a hopeless journey
   given the large number of use cases, business models, and
   constraints.

   In response to the workshop, follow-up work happened in a number of
   areas (and standardization activities are still ongoing).  Here are a
   few examples:

   o  The Light-Weight Implementation Guidance (LWIG) working group was
      created to offer a venue to collect experiences from implementers
      of IP stacks, including security protocols, in constrained
      devices.  The ability to tune IETF protocols via extensions and
      parameter choices gives implementers a lot of flexibility to meet
      the constraints of a smart object environment.

   o  The DTLS In Constrained Environments (DICE) working group was
      formed to define a DTLS profile that is suitable for Internet of
      Things applications and is reasonably implementable on many
      constrained devices, and to define how the DTLS record layer can
      be used to transmit multicast messages securely.  DTLS is seen as
      an important enabling technology for securing communication
      interactions by smart objects.

   o  A new working group has been formed to standardize an
      authentication and authorization protocol for constrained
      environments offering a dynamic and fine-grained access control
      mechanism where clients and resource servers are constrained and
      therefore have to make use of a trusted third party.  At the time
      of writing this document, the Authentication and Authorization for
      Constrained Environments (ACE) working group has just been
      started.

5.  Security Considerations

   This whole document is a report on the 'Smart Object Security
   Workshop'.  The focus of this workshop was on security only; privacy
   was not part of the workshop agenda.

6.  References

6.1.  Normative References

   [RFC6574]  Tschofenig, H. and J. Arkko, "Report from the Smart Object
              Workshop", RFC 6574, April 2012,
              <http://www.rfc-editor.org/info/rfc6574>.

6.2.  Informative References

   [PaulChilton]
              Chilton, P., "Experiences and Challenges in using
              constrained Smart Objects", March 2012,
              <http://www.lix.polytechnique.fr/hipercom/
              SmartObjectSecurity/papers/PaulChilton.pdf>.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              July 2003, <http://www.rfc-editor.org/info/rfc3552>.

   [RFC4101]  Rescorla, E. and IAB, "Writing Protocol Models", RFC 4101,
              June 2005, <http://www.rfc-editor.org/info/rfc4101>.

   [RFC4186]  Haverinen, H. and J. Salowey, "Extensible Authentication
              Protocol Method for Global System for Mobile
              Communications (GSM) Subscriber Identity Modules
              (EAP-SIM)", RFC 4186, January 2006,
              <http://www.rfc-editor.org/info/rfc4186>.

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              RFC 4949, August 2007,
              <http://www.rfc-editor.org/info/rfc4949>.

   [RFC5176]  Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
              Aboba, "Dynamic Authorization Extensions to Remote
              Authentication Dial In User Service (RADIUS)", RFC 5176,
              January 2008, <http://www.rfc-editor.org/info/rfc5176>.

   [RFC6272]  Baker, F. and D. Meyer, "Internet Protocols for the Smart
              Grid", RFC 6272, June 2011,
              <http://www.rfc-editor.org/info/rfc6272>.

   [RFC6749]  Hardt, D., "The OAuth 2.0 Authorization Framework",
              RFC 6749, October 2012,
              <http://www.rfc-editor.org/info/rfc6749>.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228, May 2014,
              <http://www.rfc-editor.org/info/rfc7228>.

   [RaspberryPi]
              Raspberry Pi Foundation, "Raspberry Pi", February 2013,
              <http://www.raspberrypi.org>.

   [SASL-OAUTH]
              Mills, W., Showalter, T., and H. Tschofenig, "A set of
              SASL Mechanisms for OAuth", Work in Progress,
              draft-ietf-kitten-sasl-oauth-18, November 2014.

   [SMART-OBJECT]
              Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson,
              "Architectural Considerations in Smart Object Networking",
              Work in Progress, draft-iab-smart-object-architecture-06,
              October 2014.

Appendix A.  Program Committee

   The workshop was organized by the following individuals:

   o  Hannes Tschofenig
   o  Jari Arkko
   o  Carsten Bormann
   o  Peter Friess
   o  Cullen Jennings
   o  Antonio Skarmeta
   o  Zach Shelby
   o  Thomas Heide Clausen

Appendix B.  Published Workshop Material

   o  Main Workshop Page
      <http://www.lix.polytechnique.fr/hipercom/SmartObjectSecurity>

   o  Position Papers
      <http://www.lix.polytechnique.fr/hipercom/SmartObjectSecurity/
      papers>

   o  Slides
      <http://www.lix.polytechnique.fr/hipercom/SmartObjectSecurity/
      slides>

Appendix C.  Accepted Position Papers

   1.   Michael Richardson, "Challenges in Smart Object Security: too
        many layers, not enough ram"

   2.   Mitsuru Kanda, Yoshihiro Ohba, Subir Das, Stephen Chasko, "PANA
        applicability in constrained environments"

   3.   Randy Bush, "An Operational View of Trust Needs of Moving
        Objects"

   4.   Andrei Gurtov, Ilya Nikolaevsky, Andrey Lukyanenko, "Using HIP
        DEX for Key Management and Access Control in Smart Objects"

   5.   Jens-Matthias Bohli, "Access Tokens for the IoT"

   6.   Martina Brachmann, Oscar Garcia-Morchon, Sye-Loong Keoh, Sandeep
        S. Kumar, "Security Considerations around End-to-End Security in
        the IP-based Internet of Things"

   7.   Kazunori Miyazawa, "Convergence of Smart Objects in industrial
        wireless sensor network"

   8.   Thomas Bartzsch, Dirk Burggraf, Laura Cristina Gheorghe, Alexis
        Olivereau, Nouha Oualha, Emil Slusanschi, Dan Tudose, Markus
        Wehner, Sven Zeisberg, "AAA-based Infrastructure for Industrial
        Wireless Sensor Networks"

   9.   Fida Khattak, Philip Ginzboorg, Valtteri Niemi, Jan-Erik Ekberg,
        "Role of Border Router in 6LoWPAN Security"

   10.  Thomas Fossati, Angelo Castellani, Salvatore Loreto,
        "(Un)trusted Intermediaries in CoAP"

   11.  Rene Hummen, Christian Roeller, Klaus Wehrle, "Modeling User-
        defined Trust Overlays for the IP-based Internet of Things"

   12.  Sam Hartman, Margaret Wasserman, "Federation, ABFAB and Smart
        Devices"

   13.  Cary Bran, Joseph Stachula, "Device Pairing: Lessons Learned"

   14.  Jan Janak, Hyunwoo Nam, Henning Schulzrinne, "On Access Control
        in the Internet of Things"

   15.  Rene Struik, "Cryptography and Security for Highly Constrained
        Networks"

   16.  Zhen Cao, Hui Deng, Judy Zhu, "The Architecture of Open Security
        Capability"

   17.  Sujing Zhou, Zhenhua Xie, "On Cryptographic Approaches to
        Internet-Of-Things Security"

   18.  Nancy Cam-Winget, Monique Morrow, "Security Implications to
        Smart Addressable Objects"

   19.  Jouni Korhonen, "Applying Generic Bootstrapping Architecture for
        use with Constrained Devices"

   20.  Olaf Bergmann, Stefanie Gerdes, Carsten Bormann, "Simple Keys
        for Simple Smart Objects"

   21.  Mohit Sethi, Jari Arkko, Ari Keranen, Heidi-Maria Rissanen,
        "Practical Considerations and Implementation Experiences in
        Securing Smart Object Networks"

   22.  Paul Chilton, "Experiences and Challenges in using constrained
        Smart Objects"

   23.  Vladislav Perelman, Mehmet Ersue, "TLS with PSK for Constrained
        Devices"

   24.  Richard Barnes, "Security for Smart Objects beyond COMSEC:
        Principals and Principles"

   25.  Rudolf van der Berg, "OECD Publication on Machine-to-Machine
        Communications: Connecting Billions of Devices", OECD Digital
        Economy Papers, No. 192, OECD Publishing

   26.  Cullen Jennings, "Transitive Trust Enrollment for Constrained
        Devices"

   27.  Barbara Fraser, Paul Duffy, Maik Seewald, "Smart Objects:
        Security Challenges from the Power Sector"

   28.  Hannes Tschofenig, "Smart Object Security: Considerations for
        Transport Layer Security Implementations"

   29.  Johannes Gilger, Ulrike Meyer, "Secure Pairing & Context
        Management"

   30.  Klaas Wierenga, "Scalable Authentication for Smart Objects"

   31.  Dirk Stegemann, Jamshid Shokrollahi, "Security in the Internet
        of Things - Experiences from Use Cases"

   32.  Alper Yegin, "Credentials for Smart Objects: A Challenge for the
        Industry"

   33.  Shahid Raza, Thiemo Voigt, Vilhelm Jutvik, "Lightweight IKEv2: A
        Key Management Solution for both the Compressed IPsec and the
        IEEE 802.15.4 Security"

   34.  Eric Rescorla, "A Brief Survey of Imprinting Options for
        Constrained Devices"

   35.  Fred Baker, "Security in distributed telemetry and control
        networks"

Appendix D.  Workshop Participants

   We would like to thank the following participants for attending the
   workshop:

   o  Jari Arkko
   o  Carsten Bormann
   o  Cullen Jennings
   o  Antonio Skarmeta
   o  Sean Turner
   o  Thomas Heide Clausen
   o  Hannes Tschofenig
   o  Michael Richardson
   o  Yoshihiro Ohba
   o  Subir Das
   o  Randy Bush
   o  Andrei Gurtov
   o  Ilya Nikolaevsky
   o  Andrey Lukyanenko
   o  Jens-Matthias Bohli
   o  Kazunori Miyazawa
   o  Philip Ginzboorg
   o  Fida Khattak
   o  Angelo Castellani
   o  Salvatore Loreto
   o  Rene Hummen
   o  Klaus Wehrle
   o  Sam Hartman
   o  Margaret Wasserman
   o  Cary Bran
   o  Jan Janak
   o  Rene Struik
   o  Zhen Cao
   o  Hui Deng
   o  Zhou Sujing
   o  Xie Zhenhua
   o  Monique Morrow
   o  Nancy Cam-Winget
   o  Jouni Korhonen
   o  Ari Keranen
   o  Paul Chilton
   o  Vladislav Perelman
   o  Mehmet Ersue
   o  Richard Barnes
   o  Rudolf van der Berg
   o  Barbara Fraser
   o  Johannes Gilger
   o  Sye Loong Keoh
   o  Olaf Bergmann
   o  Stefanie Gerdes
   o  Klaus Hartke
   o  Oualha Nouha
   o  Alexis Olivereau
   o  Alper Yegin
   o  Klaas Wierenga
   o  Jiazi Yi
   o  Juan Antonio Cordero Fuertes
   o  Antonin Bas
   o  David Schinazi
   o  Valerie Lecomte
   o  Ulrich Herberg
   o  Shahid Raza
   o  Stephen Farrell
   o  Eric Rescorla
   o  Thomas Fossati
   o  Mohit Sethi
   o  Alan Duric
   o  Guido Moritz
   o  Sebstian Unger
   o  Hans Loehr

Acknowledgements

   We would like to thank the participants and the authors of the
   position papers for their input.

   Special thanks go to Thomas Heide Clausen and Ecole Polytechnique
   (Paris) for providing the venue and organization.

   Finally, we would like to thank Rudolf van der Berg for his review
   comments.

Authors' Addresses

   Johannes Gilger
   Mies-van-der-Rohe-Str. 15
   Aachen  52074
   Germany

   Phone: +49 (0)241 80 20 781
   EMail: Gilger@ITSec.RWTH-Aachen.de


   Hannes Tschofenig
   Hall in Tirol  6060
   Austria

   EMail: Hannes.tschofenig@gmx.net
   URI:   http://www.tschofenig.priv.at