What does ‘Security’
mean for Ubiquitous
Applications?
Ross Anderson
Cambridge
Outline of Talk
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Security can help to control technical
complexity, by limiting interaction
It can help control complexity of use security usability will be a big growth area
It is also about conflict - about tussles for
commercial control, user privacy
First, let’s look at some ubiquitous
applications
Ubicomp (1) - Smart Dust
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Thousands of motes deployed in a selforganizing network for surveillance
This is in conflict with the interests of the party
under surveillance
There may be capable opponents - enemies
who deploy ‘black dust’ against your ‘white dust’
Also privacy issues - e.g. if US law prevents
monitoring US citizens without a warrant
Security partly ‘military’, partly regulatory
Ubicomp (2) - RFID
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Passive tags returning 128-bit unique ID
Story about ‘refilling your fridge’ - but at heart,
RFID is about controlling supply chains
US privacy row - can a third party scan not just
what you’re wearing but where you bought it,
when and for how much?
Triggered widespread resistance - from tradepolicy wonks to fundamentalist Christians
Serious political objection: RFID enables
manufacturers to clamp down on grey market
trading, in contravention of EU Single Market
Ubicomp (3) - in the Car
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Latest cars have 40-50 CPUs, CANBUS,
Bluetooth
Closest so far to Ubicomp ideal of computers
embedded invisibly everywhere - with a serious
attempt to make them usable, automatic etc
Growing problem of feature interaction - multiple
administrators / ‘owners’
Worries about platform vulnerability
From the privacy angle, the combination of
GSM, GPS, logging, road pricing and DRM is
bad stuff
Also, issues with aftermarket control
Ubicomp (4) - The Digital Home
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Vision (e.g. Toshiba U-home) - appliances talk
via UWB, 802.11, Bluetooth, IR, RFID
Home gateway talks broadband to the world
But trust management gets complex!
Issues of policy - multiple domains (do teens
have privacy from parents and/or vice-versa?)
Issues of practice - how do you mate the access
control /DRM systems of multiple platforms?
How can my mother manage all this stuff?
A Possible Framework
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One machine - standard computability,
complexity theories; programming tools
One person - applied psychology
One person, one machine: HCI
One machine, many people: access controls
One person, many machines (or: many apps) feature interaction, conflict, more HCI issues
Many people, many machines: more complexity,
more conflict, affecting more and more sectors
How can the security
engineer help?
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First goal: control system complexity from the
programmer’s viewpoint
Feature interaction is the fastest-growing source
of new problems
We can help ensure that one application only
interacts with another via the official interface
(compartmented operating systems, ‘Trusted
Computing’)
We can also help ensure that the application
programming interface can’t be manipulated
(API security - see my papers with Mike Bond)
VSM Attack (2000)
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Top-level crypto keys exchanged between banks in several
parts carried by separate couriers, which are recombined
using the exclusive-OR function
KP1
Source
HSM
Dest
HSM
KP2
Repeat twice…
User->HSM
: Generate Key Component
HSM->Printer : KP1
HSM->User
: { KP1 }ZCMK
Repeat twice…
User->HSM
: KP1
HSM->User
: { KP1 }ZCMK
Combine components…
Combine components…
User->HSM
: { KP1 }ZCMK ,{ KP2 }ZCMK
User->HSM
: { KP1 }ZCMK ,{ KP2 }ZCMK
HSM->User
: { KP1 xor KP2 }ZCMK
HSM->User
: { KP1 xor KP2 }ZCMK
API attack: XOR To Null Key
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A single operator could feed in the same part twice,
which cancels out to produce an ‘all zeroes’ test
key. PINs could be extracted in the clear using this
key
Combine components…
User->HSM
: { KP1 }ZCMK , { KP1 }ZCMK
HSM->User
: { KP1 xor KP1 }ZCMK
KP1 xor KP1 = 0
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Other API manipulation attacks were found on
essentially all crypto processors on the market!
New Research Problems?
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Turning TC / API security ideas into working
products will be non-trivial
Another black hole: maintainability
E.g. at present most security literature is about
bootstrapping into a secure state - once Alice
and Bob share a key, we head for the pub!
Bugs in products are not usually fixed - you are
expected to buy a new mobile phone every year.
But this won’t work for air-conditioners!
More on Maintainability
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Parallel: early software engineering work was on
producing large programs from scratch; now it’s
about evolution. Theses are no longer written on
the ‘waterfall model’ but on ‘extreme
programming’
We have almost no literature on security
resilience, and on automatic recovery after
compromise
Our own tentative ideas: ‘Smart Trust for Smart
Dust’, Anderson, Chan and Perrig, ICNP 2004
But we will need much, much more!
How can we help? (2)
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Second goal: control system complexity from the
user’s viewpoint
The current bottleneck is security usability
It’s taken 30 years to come up with (barely
adequate) ways of managing the millions of bits
of security state in a typical company
The home is more complex still!
Meanwhile, consumers have difficulty with VCR
programming and basic PC admin
Ubicomp and Usability
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U-Vision - embedded devices will be easy to
use, thus eliminating the PC’s frustrations
More sober view (Odlyzko) - trade-off between
flexibility and ease of use is different for different
users (and same user at different times/tasks)
Norman’s ‘human-centered engineering’
assumes mature products (a long way off!)
‘We will still be frustrated, but at a higher level of
functionality, and there will be more of us willing
to be frustrated’
Odlyzko’s warning
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Home environment is likely to be more
complicated than today’s office environment,
and home users generally less knowledgeable
We may have to outsource the setup and
maintenance of home appliances to experts that is, remote administration
Users given varying degrees of control,
‘depending on skills and trustworthiness’
We can already see the beginnings of this in
mobile phone and car electronics markets
Perils of Remote Admin
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I just don’t want Bill running my home!
His competitors should like it even less!
Even with open standards, there will be
severe tensions. Plumbing nightmares will
be replaced by call-centre hell
Cynical view: if the equilibrium is set by
customers’ frustration tolerance, more
usable systems means you can sell more
stuff before this point is reached
Market Demand for Usability?
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‘Microsoft has triumphed because it has
given us what we asked for: constant
novelty coupled with acceptable stability,
rather than the other way around. ...
People talk simplicity but buy features and
pay the consequences. Complex features
multiply hidden costs and erode both
efficiency and simplicity.’ (E Tenner, ‘The
Microsoft We Deserve’, NYT)
Usability and Incentives
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User sees his phone banking app not as a
Vodafone thing but a Citibank thing
If it works, Citibank gets the credit
If it doesn’t, Vodafone gets the blame
Incentives aren’t right for the app vendor
or the platform vendor
Worse - there are half-a-dozen stages in
the supply chain. Who’ll do the work?
The Right Abstractions?
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Roles, or groups?
Brands?
Locations?
Other restrictions on state?
People? (biometrics, nyms?)
Directories, or file types?
Machine owners, or file creators?
What does it mean to ‘lock the digital front
door’?
Scientific challenge
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Computer scientists have spent the last 50 years
building tools that help developers get a little bit
further up the complexity mountain
‘Risk thermostat’ - 30% of big projects fail, but
they are bigger projects each year
But the complexity that now matters most, for
building predictably dependable systems, is not
from the CPU’s viewpoint but the brain ‘s
What should we design now instead of
languages, compilers and CASE tools?
The Broader Aspects
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As everyday objects acquire intelligence, it is as
if they are under magic spells
Motorola’s phones have magic that stops them
working with other firms’ batteries
HP’s printers are under a spell that stops them
working with other firms’ ink
Microsoft’s new IRM stops Office documents
working with OpenOffice
Where will it end? How should governments
regulate a world of magic spells?
Economics of Information
Security
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Over the last four years, we have started to
apply economic analysis to information security
Economic analysis often explains security failure
better then technical analysis!
Information security mechanisms are used
increasingly to support business models rather
than to manage risk
Economic analysis is also vital for the public
policy aspects of security
Traditional View of Infosec
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People used to think that the Internet was
insecure because of lack of features –
crypto, authentication, filtering
So engineers worked on providing better,
cheaper security features – AES, PKI,
firewalls …
About 1999, we started to realize that this
is not enough
New View of Infosec
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Systems are often insecure because the people
who could fix them have no incentive to
Bank customers suffer when bank systems allow
fraud; patients suffer when hospital systems
break privacy; Amazon’s website suffers when
infected PCs attack it
Security is often what economists call an
‘externality’ – like environmental pollution
Security is also increasingly used to support
business models by locking in customers, tying
products etc
Current Security Economics
Research Topics
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Understand differences between growing and mature
markets (bargains then rip-offs; security ignored then
later used to lock in customers)
Why do people say they value privacy but act as if they
don’t?
Do we spend too little on security, or too much?
Where are the incentives misaligned, and why?
What’s the appropriate government policy?
Economics and Security Resource Page –
www.cl.cam.ac.uk/~rja14/econsec.html
The Soft World
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Effects of technology are always overestimated
short-term but underestimated long-term
Putting CPUs and comms into every thing
costing over a few bucks will change the world
Software will provide ever more of the value
Many industries will become ever more like the
software industry
We’ll get the good (flexibility), the bad
(frustration) and the ugly (monopolies)
Conclusions
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Ubiquitous computing presents many security
research opportunities
We can apply existing work in compartmented
operating systems, API security, crypto etc
We face serious new challenges in security
usability and in maintainability
Economic and policy aspects are also nontrivial security is a socio-technical system
Understanding the interplay of technical, design
and policy issues is the really hard challenge
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