 Attacks and threats  Security challenge & Solution  Communication Infrastructure  The CA hierarchy  Vehicular Public Key  Certificates

 Bogus information attack Adversaries send bogus information to influence decisions of other drivers.  Disrupt the VANET (Denial of Service) Attacker sends too many messages and jams the wireless channel.  Vehicle Tracking  Masquerading Attacker pretends to be another driver by using fake identities with malicious objectives.

Attacker reports a non-existing jam for better driving condition to himself

Attacker track another vehicle for malicious objectives

 Time sensitivity & dynamic topology Vehicles move at a fast rate.  Scalability and high density Extremely large amount of network entities  Adaptive privacy Diverse privacy degrees. Users can choose their own privacy degree.  Real-time response

 Some users misbehave or have malfunctioning equipment  Such entities should be EXCLUDED from the network in order to limit the damage caused by them

 signatures authentication › Stops malicious parties from impersonating OBUs or RSUs › Identifies misbehaving or malfunctioning vehicles  signatures verification › Prevent creation of fake vehicles › Easy removal of destroyed or misbehaving OBUs

 vehicle registration and certificate issuance  key distribution  key renewal  vehicle revocation

 Tamper-Proof Device (TPD): possesses cryptographic processing capabilities. Main responsible: 1: store cryptographic material. 2: perform cryptographic procedure. 3: sign and verify safety messages. Tamper-proof device Vehicle sensors (GPS, speed and acceleration,…) On-board CPU Transmission system ((( )))

Symmetric Approach  Online central server required  each communication require a session establishment Due to lack of a reliable online connection this approach is not suitable for VANET - messages are standalone & large scale

Public Key Approach binding public keys to corresponding identities using certificate authority Each message should :  signed with a digital signature  achieve mutual authentication without involving a server Public Key Infrastructure is the answer…….

 Safety data should be bound to vehicles certificates, In order to distinct trusted vehicles and exclude untrusted vehicles  The goal of a certificate Invalidation is to remove an untrusted vehicle. - This process is called revocation. * Multiple certificates can be bound to one vehicle

 Certificate Authorities (CAs)  CA issues certified public/private key pairs to vehicles.  The different CAs should be synchronized. Vehicles from different countries or  The preferred way: Nodes generate the key pairs and provide only the public key to CA, which will issue a certificate

Car A Car B Governmental Transportation Authorities  Governments control certification  Long certificate chain  Keys are re-certified on borders to ensure mutual certification  OBUs near each other update simultaneously  OBU needs to update its key to operate in a new region

Car A Car B Manuf. 1 Manuf. 2 Manufacturers Authorities  Vehicle manufacturers can be trusted  Only one certificate is needed  Each car has to store the keys of all vehicle manufacturers

 To authenticate each other, vehicles will sign each message with their private key and attach the corresponding CA’s certificate.  When another vehicle receives this message, it verifies the key used to sign the message and once this is done correctly, it verifies the message.

 A certificate is a vehicle’s public key and ID, signed by the CA:  Certificate = Sig-CA (PK || ID), PK, ID

 There are 4 parts:  1: message header;  2: the certificate;  3: message payload;  4:the signature of the signed message.

 Security protocols adds overhead to data transferred  Certificate are twice as large as signatures  Optimizing the distribution mechanism is a proper means of considerably reducing the over-the-air bandwidth overhead

 1–1 : Two communicating nodes will possibly establish a session. - certificates exchanged during session setup  1–n : Single node broadcasts to many nodes, without establishing a session - receiver needs to obtain the sender’s certificate before verifying the message - Sender attach its certificate to each message.

 a unique digest that can easily be computed, by applying a hash function to the certificate. When received a certificate : 1. Check If received the certificate digest in the past 2. If not : Verify Certificate 3. If verified: Store Certificate digest

 Periodic Broadcast certificate is sent in a piggy-back fashion together with a message  Certificate on demand send certificate only when not stored locally on the receiver’s side  Hybrid Certificate broadcast certificate on demand by default, until no certificate is demanded for a certain amount of time