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Secure and Efficient Network Access

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Mobile IP home registration. Mobile IPv6 correspondent node registration ... Client - home authentication in 2 RTT (identifier / challenge / response / success) ... – PowerPoint PPT presentation

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Title: Secure and Efficient Network Access


1
Secure and EfficientNetwork Access
  • DIMACS Workshop, November 3rd, 2004, Piscataway,
    NJ, USA
  • Jari Arkko
  • Ericsson Research NomadicLab
  • Pasi Eronen
  • Nokia Research Center
  • Pekka Nikander
  • Vesa Torvinen
  • Ericsson Research NomadicLab
  • This presentation has been produced partially in
    the context of the Ambient Networks Project. The
    Ambient Networks Project is part of the European
    Community's Sixth Framework Program for research
    and is as such funded by the European Commission.
    All information in this document is provided as
    is'' and no guarantee or warranty is given that
    the information is fit for any particular
    purpose. The user thereof uses the information at
    its sole risk and liability. For the avoidance of
    all doubts, the European Commission has no
    liability in respect of this document, which is
    merely representing the authors view

2
Presentation Outline
  • The Problem
  • Ongoing work
  • Some new ideas
  • An example protocol run
  • Conclusions

3
The Problem
4
Some Problems in Current Network Access
Approaches (1/3) - Efficiency
  • Attachment involves a large number of messages
  • Scanning 802.11 attachment
  • 802.1X and EAP messaging
  • 802.11i four-way handshake
  • DNA IP router and neighbor discovery
  • Address autoconfiguration, DAD
  • Mobile IP home registration
  • Mobile IPv6 correspondent node registration
  • Over 50 of this is due to security
  • Request/Response style, even across the Internet
  • Amount of data is growing with certificates,
    configuration, and discovery
  • Multiple mandatory waiting periods
  • Even a second, such as for DAD
  • Iteration over available accesses

5
Some Problems in Current Network Access
Approaches (2/3) - Security
  • Im one of the trusted network nodes approach
  • Sufficient for large cell size, well protected
    base stations
  • Not very good for devices on the coffee shop wall
  • Focus on authentication, not authorization
  • Does everyone know/agree with the service
    parameters ?
  • Denial-of-Service problems
  • Use of cryptographic keys very late in the
    process
  • Attacks that create/leave state to network side
    elements
  • Insecure lower-layer detach messages
  • 802.11 countermeasures functionality
  • Privacy protection is non-existent or incomplete

6
Some Problems in Current Network Access
Approaches (3/3) - Functionality
  • Security models do not fit all types of
    deployment
  • Credit card payments
  • Home deployments (e.g. leap of faith or physical
    connection instead of a certificate exercise)
  • Configuration, discovery, and movement support
  • What are the IP parameters that I can get from
    this access point?
  • Is my home operator available via this access
    point?
  • How much would accessing this network cost?
  • Could the network tell me when to move, and to
    what channel and parameters to use?

7
Ongoing Work
8
Ongoing Work to Address the Problems...
  • IP mobility
  • Better implementations that employ parallism
    allowed by the RFCs
  • Faster route optimization schemes, such as moving
    tasks out of the critical path
  • Address autoconfiguration
  • Turning DAD off
  • Optimistic DAD
  • DHCP and SEND security

9
Ongoing Work, Continued
  • DNA, Router and Neighbor Discovery
  • Faster algorithms for detecting whether or not
    movement has occurred
  • More frequent and precise router advertisements
  • Elimination first message delays from RFC 2461
  • SEND security
  • EAP authentication
  • Methods work (new credentials, deployment, )
  • Channel binding and parameter authentication

10
Ongoing Work, Continued
  • Link layer
  • Pre-authentication and proactive key distribution
  • Better protection of payload packets (AES etc)
  • Better information channels from the network to
    the clients (e.g., 802.21)
  • Discovery (WIEN SG)
  • Faster scanning techniques, parameter tuning
  • Bigger subnets (less IP layer work after
    attachment)
  • ...

11
Observations
  • People care about this!
  • A lot of results!
  • Most work focused on a particular slice of the
    problem
  • No good understanding of what the impact of
    individual improvement is for effiency
  • E.g., I cant afford 1 RTT in Mobile IP
  • Not enough system-level understanding of the
    security issues

12
Some New Ideas
13
Approach
  • Focus on the problem as a whole!
  • There are multiple parties involved -- not just
    two
  • Who needs to communicate with who?
  • How are the parties identified?
  • What is the optimal order of messages?
  • What system security properties are needed?
  • Are there bulk information transfer needs? How
    can they best be addressed?
  • Can we learn something from solutions in other
    contexts?

14
Caveat
  • This may not be compatible with current protocols
  • Layer-purists might object to our views
  • We do not have all the details, just pointers to
    ideas

15
Potential Solution Ingredients (1/5)
  • Addressing
  • All nodes (not just the client) need an address
  • Addresses are hashes of public keys
  • Benefits
  • All parties -- such as the access network can
    be addressed in communications
  • Avoid address stealing and functionality to bind
    addresses to credentials
  • Nodes can generate their addresses and keys on
    their own, without infrastructure
  • Privacy can be achieved via ephemeral keys
  • Identifier vs. routing semantics

16
Potential Solution Ingredients (2/5)
  • Message order
  • Find out what information the whole problem
    involves, and how many messages need to carry it
  • And re-think message order
  • Example If the clients IP address was known
    earlier, the authentication process with the
    home network could handle mobility-related
    registrations as well
  • Benefits
  • Number of messages can be reduced
  • Ping-pong delays can be avoided

17
Potential Solution Ingredients (3/5)
  • Information transfer
  • Do not fetch everything from the original source
  • Cache information about, say, roaming consortium
    in the AP
  • Learn from TCP no req-resp across the Internet
  • Either run TCP-like protocols directly between
    the client and the, say, home network
  • Or have the access point do this over the
    Internet, and use a request-response over the
    final radio hop
  • Information transfer capabilities should not be
    restricted to the initial authentication exchange
  • Benefits
  • More and faster information transfer, at any time

18
Potential Solution Ingredients (4/5)
  • Miscallenous
  • Delegation
  • Does the client have to be involved in tasks?
  • Can some tasks be delegated to the access
    point/router?
  • For instance, router based address assignment and
    DAD
  • Even a mobility related registration could be
    delegated
  • Denial-of-Service protection
  • No separation to attachment and secure
    attachment
  • Stateless design on the network side

19
Potential Solution Ingredients (5/5)
  • Miscallenous, continued
  • Privacy protection
  • Build the protocols for non-static identifiers
    and addresses
  • Protect communications from the start, not at the
    end

20
An Example Protocol Run
21
The Example
  • Flows
  • Current message flow
  • Suggested basic message flow
  • Variant with better mobility support
  • Handoff
  • Assumptions
  • Authentication needed roaming case
  • IPv6
  • Mobility with RO one peer
  • Client - home authentication in 2 RTT (identifier
    / challenge / response / success)

22
Example Current Flow
23
(No Transcript)
24
Example Improved Basic Flow
25
Beacon includes - Access node identifier -
Access network identifier - Possible other
advertised information, such as capabilities,
roaming partner identifiers, and so on
26
Beacon
The functions of the secure attachment
protocol - Authenticate the claimed identities
(opportunistically) - Turn ciphering on, as in
802.11i 4-way handshake It also piggybacks the
following - Deliver IPv6 router advertisements -
Authentication and authorization to the home
(partially) - May perform address allocation on
behalf of the client - May perform mobility
registration on behalf of the client
27
Beacon
I1 trigger exchange
--------------------------gt

select pre-computed R1 R1
puzzle, D-H, key, sig
lt------------------------- check sig
remain
stateless solve puzzle I2
solution, D-H, key, sig
--------------------------gt compute D-H
check cookie

check puzzle
check sig
R2 sig
lt-------------------------- check sig
compute D-H
28
Beacon
Secure Attachment
Home auth authz
- The home authentication process follows the
identity/challenge/response/success model (for
instance) - A mobility protocol home registration
is carried in the same messages -- executed after
the final response message is sent
29
Beacon
Secure Attachment
Home auth authz
RO registration
1. Client delivers its public key, other
parameters, and a statement that delegates the
access network to allocate an address for it. 2.
Access network has a statement from an authority
about the prefixes it owns. It constructs an
address and sends the address, the statement, and
the clients information to the home network. 3.
Home network sends the information along to the
correspondent node. Correspondent node believes
the validity of the care-of address since it
trusts the same authority. in a HIP-like mobility
solution there is no need to verify the home
address clients signed statement is sufficient.
30
Example Variation with Better Mobility Support
31
Beacon
Secure Attachment
Home auth authz
RO registration
Care-of Address Test
Variation A common authority can be avoided by a
care-of address test.
32
Example Handoffs
33
access node 2
Beacon
Secure Attachment
- Access node 1 has a signed statement from the
access network that it is a part of the network.
This is given to the client. - After
authentication and authorization at the home
network, a set of explicit authorization criteria
are known. A signed statement is given to the
client, saying that the client is allowed to move
to another access node within the same network,
as long as the criteria are fulfilled.
34
access node 2
Beacon
Secure Attachment
Secure Attachment
- Access node 2 has a similar statement from the
access network as well. - Client presents its
statements and the usual home authentication/autho
rization process can be skipped. Client gets
access. - However, access node 2 needs to verify
authorization criteria. In many case this implies
contacting a central node in the access network
(e.g. concurrent usage limit).
35
Conclusions
36
Conclusions
  • Need to look at the whole problem
  • Measurements
  • System-level security story
  • Solutions
  • Some early solution ideas presented
  • Clearly more work is needed for the details,
    security analysis actual benefits
  • Feedback appreciated!
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