Ad-Hoc Networks

1
Ad-Hoc Networks
Establishing node-to-node communication with no
infrastructure needed
Authors

• Ðorde Trifunovic, djole_at_europemail.com
• Nikola Milanovic, nikola99_at_EUnet.yu
• Prof. Dr. Veljko Milutinovic, vm_at_etf.bg.ac.yu

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What will you learn from this tutorial?
This tutorial will guide you through the
following sections

• Introduction
• Mobile networks
• Routing in ad-hoc networks
• Security in ad-hoc networks
• Bluetooth
• The IEEE/UB ad-hoc multihop sensor network and
  Bluetooth lessons learned from the research by
• Gvozden Marinkovic (mgvozden_at_eunet.yu)
• Aleksandar Radovanovic (biblbroks_at_sezampro.yu)
• Aleksandar Beric (alberic_at_eunet.yu)
• Branislav Cukanovic (chuka_at_beotel.yu)
• Nikola Milanovic (nikola99_at_eunet.yu)

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Introduction to Ad-Hoc Networks
Evolution of network communications A new
stage
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Introduction

• Two basic groups of ad-hoc networks
• Networks of mobile computers handled by users
• Wireless sensor networks
• Basic characteristic ability to establish
  network communication between hosts without any
  infrastructure needed.
• The most significant advance compared to classic
  fixed systems
• Reveals a very large scale of new possibilities

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Introduction

• Ad-hoc networks may be considered as a new stage
  in evolution of network communications
• Fixed computer networks
• Concepts and mechanisms educed and amended for
  long time
• Lot of experiences acquired
• A useful base for origin and development of
  mobile networks...

6
Introduction

• Wireless communication has its peculiarities.
• Taking the already developed solutions is not
  possible.
• In the beginning modifications and adaptations
  of existing mechanisms.
• Later more and more of new ideas, relieved from
  the ballast of obsolete concepts.

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Mobile Networks
Meet the family
8
Mobile Networks

• Not long time ago, mobile networks were treated
  just as extensions of fixed networks.
• Actors are
• Fixed hosts (FH)
• Mobile hosts (MH)
• Base stations (also known as mobility support
  routers MSR)

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Mobile Networks

• Mobility Support Router (MSR)
• Every MSR supports the area limited by its range
  (wireless cell).
• MSR can communicate with MHs currently located in
  its cell.
• MHs directly communicate only with MSRs
• MHs can freely move from one cell to another

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Mobile Networks

• Sending packets from FH to MH
• MSRs are bridges between the wired network and
  mobile hosts.
• When some fixed host (FH) wants to send a packet
  to a mobile host (MH), communication is divided
  into two parts
• Standard communication inside the fixed
  network,from FH to the proper MSR
• Wireless communication between MSR and MH.

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Mobile Networks

• Hiding mobility
• Mediation of MSR is entirely transparent to FH.
• For this kind of communication, indirect
  protocols were developed, with the purpose of
  hiding mobility from immobile hosts.

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Mobile Networks

• One-hop wireless communication
• Direct communication between mobile hosts does
  not exist
• Mobility is very limited and dependant on the
  existing wired infrastructure
• MHs can move only within areas determined by the
  range of MSR, as well as by the range of its own
  transmitter
• Mobility is limited to only one hop between
  mobile host and fixed network
• Anyhow, a step towards real, multihop wireless
  networks.
• Nature of wireless communications had to be
  considered
• Later was of great benefit for development of
  ad-hoc networks

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Mobile Networks

• Nature of wireless communications
• Wireless vs wired links
• Slower
• Less reliable
• Prone to loss of signal due to noise and fading
• With much more limited bandwidth
• With much more frequent occurrence of asymmetric
  quality of communication
• Mobile hosts are often disconnected from the
  fixed network for short or long periods of time
• Moving out of range
• Exhausted battery

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Mobile Networks

• Realizations and usage possibilities
• Wireless Local Area Network (WLAN)
• Connecting mobile and portable computers to
  existing widely used fixed networks like the
  Internet

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Mobile Networks

• Drawbacks and limitations
• Infrastructure is needed
• Requires large investments
• Time consuming installation
• Communication cannot be always established where
  needed
• Expensive maintenance

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Mobile Networks

• In many cases it is necessary to establish a
  connection even if infrastructure does not
  exist, or is damaged.
• Typical example alarming rescuers in case of
  earthquake, flood, war destruction
• Communication must be established without any
  preliminary setup (ad-hoc).

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Mobile Networks

• Ad-Hoc Networks
• Mobile hosts can communicate between each other
  on much greater distances than covered by their
  ranges.
• That is practicable thanks to presence of other
  mobile hosts that can be reached by the source
  host, and that are willing to retransmit its
  packets further on
• Thus, propagating from one MH to another,
  packets are conveyed to the destination
• That is how multihop wireless communication
  through a temporally formed ad-hoc network is
  realized.

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Routing in Ad-Hoc Networks
How to find the right way?
19
Routing in Ad-Hoc Networks

• Efficient routing of packets
• In conventional networks, the most widely used
  routing algorithms are such as distant vector or
  link state
• Periodical broadcast, with the purpose of
  keeping routing tables up-to-date
• In some cases those algorithms were adapted to
  be used in ad-hoc networks
• We will just mention two representatives
• Destination-Sequenced Distance-Vector (DSDV)
• Wireless Routing Protocol (WRP)
• Benefit Route to every host in the network is
  always known. But

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Routing in Ad-Hoc Networks

• Drawbacks of adapted conventional routing
  algorithmsseem to be of much more significance
  than the benefits
• Large bandwidth overhead
• Batteries quickly become exhausted
• Significantly reduced scalability
• Unneeded cumulation of redundant routes
• Often not able to quickly enough respond to
  dynamics of changes in systems in which the
  hosts can move

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Routing in Ad-Hoc Networks

• On-demand routing protocols
• Because of specified constraints of said
  solutions,we are going to pay more attention on
  another approach,which is fundamental for the
  so-called on demand routing protocols.
• We will shortly describe three of those
  protocols, which attack the problem from
  different standpoints,introducing different
  assumptions and diversely prioritising problems
  that are to be solved
• Dynamic Source Routing (DSR)
• Ad-Hoc On-Demand Distance Vector Routing (AODV)
• Temporally Oriented Routing Algorithm (TORA)

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Routing in Ad-Hoc Networks

• All the proposed solutions contribute to the
  apparent reclamation of performance, compared to
  classic algorithms, which work much better in
  the stationary environment for which they were
  designed in the first place.
• Algorithms that will be presented here are just
  specimens of a large number of solutions
  developed by now (ietf.org).
• New algorithms are still being developed and
  evolved.

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Routing Protocols - DSR

• 1. Dynamic Source Routing (DSR)
• Based on the concept of source routing
• Sender provides the sequence of nodes through
  which the packets will be sent
• Sequences are held in route cache that every
  host must maintain for itself
• Route is determined dynamically, when it is
  needed
• There are no periodical advertisements of routers
• Instead, every host initiates route discovery
  when it needs to send a packet to another host
  for which initiator does not have the associated
  route in its cache

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Routing Protocols - DSR

• Route Discovery route request
• Initiated by sending a route request packet
• Propagates through the network until it reaches
  the destination host (if the route exists)
• On its way, it collects addresses of all visited
  hosts, and stores them into its route record

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Routing Protocols - DSR

• Route Discovery route reply
• The first route request packet that arrives to
  destination is accepted, its route record is
  copied and returned to the initiator using the
  route reply packet.
• Destination host returns the route reply to the
  initiator of route discovery, using the route
  from its own cache.

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Routing Protocols - DSR

• Route Discovery route reply (2)
• If destination host does not have a route to the
  source host in its cache, there are two options
• Route reply is returned using inverse route that
  was found by the route request packet
• Destination host initiates route discovery to
  find a route to the original initiator.
• First option requires symmetric links
• Transfer quality must be the same in both
  directions
• But that is often not the fact in mobile
  communications.

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Routing Protocols - DSR

• Route Discovery route reply (3)
• Second opportunity (inverse route discovery,
  from destination to source) is more significant
• Providing support for non-symmetric links (very
  important merit of this algorithm).
• I that case, the original route reply must be
  sent together with new route request, i.e.
  attached to it (that is called piggybacking)

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Routing Protocols - DSR

• Route Maintenance
• Implemented by acknowledgements and route error
  packets.
• Acknowledgements may be
• hop-by-hop links must be symmetric
• end-by-end important when links are not
  symmetric

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Routing Protocols - DSR

• Route Maintenance (2)
• When using hop-by-hop acknowledgement
• Host which did not get acknowledgement for its
  retransmissionsends route error packet with
  information about hop that broke down
• Upon that error packet, source host truncates
  routing tree being held in its cache, at the
  point of that hop
• When using end-by-end acknowledgement
• Information about the point of breakage does not
  exist
• Source host may only assume that the last hop is
  broken.

?
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Routing Protocols - DSR

• Modifications / Optimisations
• Various modifications and amendments of this
  algorithm are feasible.
• Well mention just one of them capability of
  working in the so-called promiscuous receive
  mode
• Host auscultate packets that were sent to other
  hosts, and updates its own cache according to
  the information thus received
• This, however, causes more power to be used and
  more rapid battery discharge .

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Routing Protocols - DSR

• Summary DSR merits
• Ability to work with asymmetric links.
• No periodical routing advertisement
• Enables bandwidth and energy conservation
• Overhead does not exist when there are no
  changes in the network.
• Can be easily improved to become able for
  providing multiple routes
• That way, it is not always necessary to initiate
  new route discovery when some link breaks.

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Routing Protocols - DSR

• Summary DSR drawbacks
• Caused by the nature of source routing.
• Large bandwidth overhead
• Route request packets rapidly grow as they
  propagate through the network(in their route
  records they store information about every host
  over which they passed)
• That causes potential huge route reply packets
• Also larger message packets, because addressing
  demands the whole route to be specified.
• Scalability problems acceptable size of the
  network is limited
• Diameter of the network (the largest number of
  hops needed for communication between any two
  hosts in the network)directly refers to
  bandwidth overhead.

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Routing Protocols - DSR

• Summary
• Dynamic Source Routing protocol is suitable for
  appliance in ad-hoc networks
• with moderate numbers of mobile hosts
• which move with moderate velocities.

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Routing Protocols - AODV

• 2. Ad-Hoc On-Demand Distance Vector Routing
  (AODV)
• New route is discovered in a manner that looks
  similar to route discovery by DSR
• Source host (src) broadcasts route request (RREQ)
  to all of its neighbours when needs to discover
  route to some destination host (dst)
• Then, it waits for route reply (RREP).
• But similarity is discontinued at this point.

?
35
Routing Protocols - AODV

• Route Request
• Sequence number
• Number that every host generates for itself.
• It is incremented every time when something is
  changed in adjacency (e.g., when some link
  breaks).
• For every route, destination sequence number
  (DSN) is stored in the routing table
• Last DSN that src earlier knew for any route to
  dst, is sent in RREQ, together with current
  sequence number of src and other information
  needed RREQ (src, dst, srcSN, dstDSN, )

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Routing Protocols - AODV

• RREQ does not contain the route record
• Does not collect information about hosts through
  which it propagates
• Remembers only the number of hops.
• Instead, the host through which RREQ propagates
  adds inverse route (towards src) to its routing
  table
• Stores, together with other relevant information,
  the address of the neighbour (n1) that sent RREQ
  to it
• If that host later receives relevant RREP, it
  will automatically know that reply should be
  transferred to the neighbour (n1)
• In that case, it also records the address of the
  neighbour (n2) that sent RREP, thus establishing
  route towards dst.

n1
n2
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Routing Protocols - AODV

• Instead of recording the whole route, as with DSR
  applied, host here keeps only next hop (among
  other relevant information about some
  destination), i.e. address of its neighbour to
  which it transfers packets addressed to the
  destination

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Routing Protocols - AODV

• Route Reply
• When RREQ reaches a host that has a route to dst,
  comparison of DSNs from the packet and from the
  routing table is made
• If DSN from RREQ is greater ? the hosts route
  to dst is not recent enough ? the host
  rebroadcasts the request
• Otherwise, the host returns RREP to src, with
  the calculated information about the discovered
  route (total hop count, lifetime that remains),
  among which more recent DSN, copied from the
  routing table of the host.

DSN(dst)8
DSN(dst)12
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Routing Protocols - AODV

• RREQ may reach dst itself, and then dst returns
  RREP to src.
• Anyway, RREP is returned using inverse route
  formed by intermediate hosts during the
  propagation of RREQ.

dst
src
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Routing Protocols - AODV

• Route Maintenance
• For every route that a host is acquainted with,
  it maintains the list of neighbours that use
  that route, so that it is able to notice them
  about eventual link breakage on the route.
• Link breakage is detected by the absence of
  hello messages, which must be emitted by every
  host after the specified time interval expires.

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Routing Protocols - AODV

• Summary Advantages of AODV over DSR
• Significantly smaller network bandwidth
  overhead
• Both control and message packets are smaller
• The reason is the requirement of only two
  addresses when routing (destination and next
  hop), instead of the whole route as with
  sequenced routing
• This is good for scalability, because the size
  of a packet does not depend on the network
  diameter.
• Provides support for multicasting.

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Routing Protocols - AODV

• Summary AODV drawbacks
• Works only with symmetric links.
• Hosts must periodically advertise hello messages
• Increased bandwidth overhead
• Reduced possibility of energy conservation by
  remaining in the sleep mode.
• Does not support multi path routing(offers only
  one route per destination)
• Every time when some link on the route breaks,
  new route must be discovered
• Increased probability of congestion.

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Routing Protocols - TORA

• 3. Temporally Oriented Routing Algorithm (TORA)
• Offers an interesting approach to problem
  solution.
• Conceived as link-reversal algorithm.
• The idea is to define topology of a network
  using a directed acyclic graph (DAG)
• Hosts represented as nodes and with directed
  links
• Direction of link is realized by assigning
  height to every node, so that the link is
  directed from the node with greater height to
  the node with lower height.

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Routing Protocols - TORA

• General idea
• The destination node should have the minimal
  height in the graph.
• Other nodes get greater and greater height as
  the distance from the destination grows.
• Packets may be sent only from higher to lower
  nodes, i.e., only via downstream links.

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Routing Protocols - TORA

• DAG Forming
• Starts when node that does not have downstream
  links wants to send a packet to a destination
  node.
• Initially, all nodes in the graph have
  undetermined height (NULL), except the
  destination node that has the height of ZERO
  (which is considered less even from NULL).
• Source node then broadcasts QRY packet to its
  neighbours.
• QRY packet propagates through the network,
  marking every node over which it passes as
  interested for route discovery by setting its
  route request flag.

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Routing Protocols - TORA

• When QRY packet arrives to a node that has at
  least one downstream link, the node then emits
  the UPD packet.
• UPD propagates back through the network, setting
  the height to all nodes with the route request
  flag set,at the same time resetting those flags.
• Every further node gets greater height then the
  precedent one on the path of the UPD propagation.

dst
src
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Routing Protocols - TORA

• Many downstream links can lead to the same
  destination.
• Algorithm enables multiple path routing.

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Routing Protocols - TORA

• In case of link break
• If the node still has downstream links left, no
  action is performed
• Otherwise, the node broadcasts a UPD packet, thus
  recovering DAG
• Recovering is a one-pass process, except in the
  case of network partitioning

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Routing Protocols - TORA

• Advantages of TORA
• Fast route discovery
• Multiple path routing
• Recovering is localised
• Multicast support
• Lightweight Adaptive Multicast (LAM) algorithm

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Routing Protocols - TORA

• Downsides of TORA
• Requires external timing mechanism (GPS)
• DAG becomes less optimal as the time passes
• Can be solved using refresh packets

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Routing Protocols - TORA

• TORA is designed for
• Large networks
• Many nodes with dense distribution

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Issue of Security in Ad-Hoc Networks
There is no need to see his identification...
53
Attributes of security

• The attributes of security are
• Availability
• Confidentiality
• Integrity
• Authentication
• Non-repudiation.

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Attributes of security

• Availability ensures the survivability of
  network services despite denial of service
  attacks.
• A denial of service attack could be launched at
  any layer of an ad hoc network.
• On the physical and media access control layers,
  an adversary could employ jamming to interfere
  with communication on physical channels.
• On the network layer disruption of the routing
  protocol can cause a break of the network.

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Attributes of security

• Confidentiality ensures that certain information
• is never disclosed to unauthorized entities.
  
• Leakage of information could have devastating
• consequences.
• Routing information must also remain confidential
  in some cases.

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Attributes of security

• Integrity guarantees that a message being
  transferred is never corrupted.
• A message could be corrupted because of benign
  failures, such as radio propagation impairment,
  or because of a malicious attacks on the
  network.

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Attributes of security

• Authentication enables a node to ensure the
  identity of the peer node it is communicating
  with.
• Without authentication, an adversary could
  masquerade a node, thus gaining unauthorized
  access to resource and sensitive information and
  interfering with the operation of other nodes.

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Attributes of security

• Non-repudiation ensures that that the origin
• of a message cannot deny having sent the
  message.
• Non-repudiation is useful for detection and
  isolation of compromised nodes.

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Challenges and opportunities

• Attacks ranging from passive eavesdropping to
  active impersonation, message replay, and message
  distortion.
• Eavesdropping might give an adversary access to
  secret information, violating confidentiality.
• Active attack might allow the adversary
• to delete messages,
• to inject erroneous messages,
• to modify messages, and
• to impersonate a node
• Violating availability, integrity,
  authentication, and non-repudiation.

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Challenges and opportunities

• We should take into account the attacks launched
  from within the network, by compromised nodes.
• The ad-hoc networks should have a distributed
  architecture with no central entities.
• Introducing any central entity into our security
  solution could lead to significant vulnerability.

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Challenges and opportunities

• There are two sources of threats to routing
  protocols
• from external attackers
• from compromised nodes

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Challenges and opportunities

• Detection of incorrect information is difficult
• Outdated routing information
• False routing information generated by
  compromised nodes
• could be considered as the outdated
  information
• If routing protocols can discover multiple
  routers, nodes can switch to an alternative route

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Challenges and opportunities

• Another way is to use diversity coding
• Diversity coding takes advantage of multiple
  paths in an efficient way, without message
  retransmission
• Even if certain routes are compromised, the
  received node may still be able to validate and
  to recover messages

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Challenges and opportunities

• Cryptographic schemes
• digital signature
• public and private keys
• Key management service
• A public key infrastructure is superior in
  distributing keys and in achieving integrity and
  non-repudiation.
• In a public key infrastructure, each node has a
  public/private key pair.
• Public keys can be distributed to other nodes,
• while private keys should be kept
  confidential
• to individual nodes.

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Challenges and opportunities

• There is a trusted entity called Certification
  Authority (CA) for key management.
• The CA has a public/private key pair
• Public key is known to every node
• CA signs certificates binding public keys to
  nodes
• The trusted CA has to stay on-line to reflect the
  current binding
• Although no single node is trustworthy in an ad
  hoc network we can distribute trust to an
  aggregation of nodes.
• Assuming that any t1 nodes will unlikely be all
  compromised, consensus of at least t1 nodes is
  trustworthy.

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Challenges and opportunities

• This is the principle of distributed trust.
• To accomplish distribution of trust in key
  management service one can use threshold
  cryptography.
• An (n,t1) threshold cryptography
  scheme allows n
  parties to share the ability to perform a
  cryptographic
  operation (e.g., creating a
  digital
  signature), so that any t1 parties
  
  can perform this operation jointly,
  whereas it
  is infeasible for most t
  parties to do so,
  even by collusion.

67
Challenges and opportunities

• We divide the private key k of the service into n
  shares (s1,s2,,sn), assigning one share to each
  server.
• Each server generates a partial signature for the
  certificate using its private key share
• With t 1 correct partial signature, the
  combiner is able to compute the signature for the
  certificate.
• Compromised servers cannot generate correctly
  signed certificates by themselves

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Challenges and opportunities

• A combiner can verify the validity of a computed
  signature using the service public key.
• In case verification fails the combiner tries
  another set of partial signatures.
• A problem with threshold cryptography is that it
  assumes synchronous system and an ad hoc network
  is asynchronous by its nature
• Any synchrony assumption is a vulnerability in
  the system
• Fortunately there is an asynchrony prototype of
  such a key management service, which has been
  implemented recently.

69
Summary

• An ad hoc network is very vulnerable to many
  kinds of attacks.
• We have to protect not only the data, but also
  the routing information.
• The best way for that is a cryptography scheme
  with public/private key management, combined
  with distribution of trust.
• But it is not cheap and it is complex.
• A lot of things still have to be done in this
  area in the future.

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Bluetooth
Following the steps of King Harald...
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Bluetooth
Special Interest Group (SIG)

• Ericsson Mobile Communications AB
• IBM Corp.
• Intel Corp.
• Nokia Mobile Phones
• Toshiba Corp.

72
Bluetooth
Bluetooth wireless technology

• Open specification for short-range wireless
  connectivity
• Effortless, instant connections
• Wide range of communication devices
• Based on a radio link
• Facilitates fast and secure transmission of both
  voice and data
• Operates in a globally available frequency band

73
Bluetooth
Bluetooth module

• ports (USB, UART, PCM)
• baseband
• voltage regulator
• crystal
• radio
• antenna interface
• flash

74
Bluetooth

• External interfaces
• USB 1.1 (12 Mbps), full USB slave functionality
• UART (Rx, Tx, RTS and CTS), 460.8 kbs
• PCM (sync 8kHz, clock 200kHz-2MHz)
• Antenna Interface
• 50 ohm Bluetooth ISM band antenna (2.4 - 2.5 GHz)

75
Bluetooth

• Communication layers
• Base Band (BB)
• Link Manager (LM)
• Host Controller Interface (HCI)
• Additional software
• L2CAP
• RFCOMM

76
Bluetooth

• Base Band General Description
• Frequency hop transceiver
• Shaped, binary FM modulation
• Symbol rate is 1 Ms/s
• Slotted channel is applied with a nominal slot
  length of 625 ms.
• Time-Division Duplex (TDD) scheme
• Information is exchanged through packets
• Each packet is transmitted on a different hop
  frequency
• Combination of circuit and packet switching.

77
Bluetooth

• Bluetooth can support
• Asynchronous data channel
• Up to three simultaneous synchronous voice
  channels
• Channel which simultaneously supports
  asynchronous data and synchronous voice

78
Bluetooth

• Bluetooth system consists of
• Radio unit
• Link control unit
• Link management and host terminal interface
  functions

79
Bluetooth

• Connection types
• point-to-point
• point-to-multipoint

• Master/slave communication
• piconets
• scatternets

80
Bluetooth

• Other features
• Link Manager Protocol
• Logical Link Control
• Service Discovery Protocol
• RFCOMM
• IrDA
• Telephony Control Protocol
• ...

Potential platform for ad-hoc network
realization!
81
Design of ad-hoc multihop sensor net with
Bluetooth Lessons learned
How to make your electronic devices cooperate
with each other?
82
Introduction

• The main goals of this project
• Creating hw/sw specification for replacing and/or
  upgrading the existing wire systems for data
  acquisition and process control
• Development of routing protocol
• Connecting Bluetooth with a microcontroller
  (router)
• Integration of routing protocol on the base
  Bluetooth chip
• Universal platform for wireless integration
• Stable and universal hardware platform
• Reliable and easy replaceable software

83
System Overwiev

• An open data acquistion system, based on wireless
  
• ad-hoc multihop sensor network
• Routing protocol
• Interface and routing module (IFRM)
• Personal Digital Assistant (PDA)
• Digital Signal Processing System (DSPS)
• Software for data acquisition (Shell)
• Internet accessible database

84
System Overview
85
System Overview

• Basic advantages
• Universal and open platform
• Can be implemented in any environment
• Possibilites of use
• Factories
• Power plants
• Health-care institutions
• Rescue actions
• Research of inhospitable terrain

86
System Overview

• Main problems
• Providing critical data transmission rate
• Stable ad-hoc networks
• Proposed solutions
• Bluetooth technology
• Designed routing protocol

87
Implementation - routing protocol

• Designed with the following guidelines
• speed
• reliability
• simplicity
• Existing solutions considered
• DSR
• AODV
• TORA

88
Implementation - routing protocol

• The routing algorithm defines three types of
  messages
• Route Request (RREQ)
• Route Reply (RREP)
• Route Error (RERR)

89
Implementation - routing protocol

• Route Request

90
Implementation - routing protocol

• Route Reply

91
Implementation - routing protocol

• Route Error

92
Implementation - routing protocol

• Functioning of the protocol
• Master
• Gateway
• Slave

93
Implementation - routing protocol

• Possible network topology

94
Implementation - routing protocol

• System initialization
• Forming of piconets
• Creation of neighboor tables
• Initialization of empty routing tables

95
Implementation - routing protocol

• Routing table entry

96
Implementation - routing protocol

• Sending RERR
• Link is broken
• No active route to destination
• RRER is received from a neigboring node

97
Implementation - routing protocol

• Simulation
• Starting topology specified in the configuration
  file
• Number of nodes is not limited
• For each node, a separate thread of execution is
  created
• Messages and destinations are being generated in
  random fashion
• Traversing of nodes between piconets

98
Implementation - routing protocol

• Process of route discovery (RREQ forwarding)

99
Implementation - routing protocol

• Process of route discovery (RREP forwarding)

100
Implementation - routing protocol

• Usability analysis
• Advantages compared to classic broadcast
  algorithms

101
Implementation - routing protocol

• Usability analysis
• Elimination of redundant piconets

102
Implementation - IFRM

• The routing protocol was implemented
• in a separate hardware module
• Serial (UART) connection with Bluetooth
• HCI level

103
Implementation - IFRM

• The main functions of IFRM
• Forming of a wireless multihop ad-hoc network
• Link maintenance
• Packet routing
• Route discovery
• Providing a transparent interface between the
  ad-hoc network and any serial (RS-232) device
• Providing PDA functionality

104
Implementation - IFRM

• The architecture of IFRM

105
Implementation - IFRM

• Routing protocol - host side
• The modified AODV protocol, with the following
  restrictions
• Size of routing tables is limited to 79 entries
• Communication in the network is server centric

106
Implementation - IFRM

• Routing protocol - host side
• The modified AODV protocol, with the following
  restrictions
• End-to-end flow control is omitted
• CRC checking and retransmission are not
  implemented
• Packet sequence is not checked
• Restrictions due to fact that Bluetooth modules
  do not conform to the Bluetooth V1.0B
  specification

107
Implementation - IFRM

• Routing protocol - host side
• Assumptions due to uncomformance to V1.0b
  specification
• In course of full-duplex communicationthere is
  no implicit master-slave switch
• Inquiry and paging are possible without
  interfering with the current transmission
• Only the master can broadcast on the piconet
• A node can transparently be a member in more
  piconets(Bluetooth baseband controller is
  capable of transparent TD multiplexing)
• It is possible to have more than 7 nodes in a
  piconet(parking and unparking is done
  transparently by the baseband controller)

108
Implementation - IFRM

• Routing protocol - host side
• Bugs and workarounds
• Sending two consecutive broadcast packets causes
  a reset
• During maximum full-duplex transfer, packets or
  parts of the packets disappear

109
Implementation - IFRM

• Connection of IFRM with the mobile host

110
Implementation - IFRM

• Routing protocol - server side
• No routing module
• The software performs routing
• Special mechanism for implicit destination
  address discovery

111
Implementation - IFRM

• Routing protocol - server side
• Communication with Bluetooth
• TCP ports
• For each mobile host exists a corresponding TCP
  port on the sever
• Port numbers start from 10 000
• All communication is performed over the TCP/IP
  connections on these ports
• The mapping of ports and hardware addresses of
  Bluetooth modules is static

112
Implementation - PDA

• The role of PDA is to provide mobility to the
  expert.
• PDA is capable of receiving two types of
  messages
• Sensors have reported irregular data, but expert
  system managed to stabilize the system. The
  confirmation is required.
• Sensors have reported irregular data and expert
  system did not manage to stabilize the system.
  The remote command and presence is required.
• PDA is capable of sending two types of messages
• Confirmation of received warning
• Command that initiates some action in the system,
  based on received data
• In this phase, the internal battery supply is not
  designed.

113
Implementation - DSPS

• DSPS is realised as an example of device
• that can be connected to this platform.
• Based on TI Digital Signal Processor
• Gathering of information from different
  peripherals
• Real-time processing
• Transferring data to server over IFRM

114
Implementation - DSPS

• The DSPS architecture

115
Implementation - DSPS

• DSPS Communication
• Standard RS-232 connection (MAX3225cpp)
• CAN driver
• Synchronous Serial Interface (SPI)

116
Implementation - DSPS

• DSPS function
• Finding spectrum of some analog signal using FFT
• Transferring data to server via transparent
  ad-hoc network
• Receiving commands from the system, thus
  creating positive feedback system

117
Implementation - Shell

• Multipurpose software platform
• Data acquisition
• Decision making
• Signal processing
• Slarming
• Tracking the current stateof the system
• Database administration

118
Implementation - Shell

• Communication with sensors
• TCP/IP ports
• Two-way socket communication
• Conformance to IEEE 999-1992. SCADA specification

119
Implementation - Shell

• System configuration
• Type of the sensor
• Name of the sensor
• Factory address of corresponding Bluetooth
  module
• Range of allowed values

120
Implementation - Shell

• Readings display
• Simple view
• Graph view
• Real-time monitoring
• History

121
Implementation - Shell

• Spectrum analysis

122
Implementation - Shell

• Database
• Realized with MySQL Server
• ODBC
• Flexible, DBMS independent

123
Implementation - Shell

• Expert System
• Monitoring (controlling)
• Knowledge base
• Algorithm of direct chaining
• Based on preconditions (sensor readings) and
  using the rules, the expert system reaches a
  decision
• Depending on the actual application, any expert
  system with its knowledge base can be easily
  integrated

124
Implementation - Internet connectivity

• The system database can be accessed from a Web
  client,
• with the purpose of shortening the response time.
• MySQL Server
• PHP 4.0.4
• Apache Web Server 1.3.14

125
Implementation - Internet connectivity

• Standard three-tier architecture is used

126
Implementation - Internet connectivity

• Web client access
• Username and password
• Choosing between sensors
• Formulating search queries
• by time
• by value
• Extending the system towards full Internet
  automation

127
Testing and integration

• Separate component testing
• Routing protocol
• IFRM
• DSPS
• PDA
• Shell
• Database
• Internet connectivity

128
Testing and integration

• Component integration
• Shell and database
• Internet access
• Communication between Shell and IFRM

129
Testing and integration

• Final integration
• Modification of the simulator
• Testing IFRM in the network with more than 100
  nodes
• Integration of DSPS

130
Summary

• Indicating a new course of development of
  wireless communication
• Integration of different electronic devices in a
  single information network
• Open system any device capable of serial
  communication can be connected
• Creation of custom ad-hoc networks
• Java-enabled microcontrollers
• Integration of the routing protocol on the
  Bluetooth baseband
• Possible improvements
• Additional research of the routing protocol
• Testing IFRM in real-world working conditions
• Making software even more modular
• Development of several classes of sensors
• Potential GPS integration
• Internet automation