SPLASH Sécurisation des ProtocoLes dans les réseAux mobileS ad Hoc 12 Décembre 2003 Refik Molva Institut EURECOM

MANET Security Requirements Wireless & Mobile Limited Energy Lack of physical security Ad Hoc Lack of(or limited) infrastructure Lack of a priori trust Cooperation Enforcement Secure Routing Key management [Recent security solutions for mobile ad hoc networks In “Ad Hoc Networks” IEEE Press - Wiley Ed]

Key Management Objectives Bootstrapping from scratch Fully distributed Minimum dependency

Key Management Approaches Symmetric crypto [Basagni et al.] (ID, PK) binding –Certificate = (ID,PK) CA Self-organized Authorities [Zhou, Haas] [Kong, et al.] [Yi, Kravets] [Lehane, et al.] Web of trust(PGP) [Hubaux, Buttyan, Capkun] –Certificate-less Crypto-based IDs: ID = h(PK) [Montenegro, Castellucia] [O’Shea, Roe] [Bobba, et al] ID-based Crypto: PK = f(ID) [Halili, Katz, Arbaugh] Context-dependent authentication –location-limited channels [Balfanz, et al.] –Shared passwords [Asokan, Ginzborg]   

Self-organized Admission Control Performance Comparison Centralized (simple signatures) –member gets t signatures from other members –Server grants GMC when t or more signatures are shown. Distributed (threshold signatures) –member gets “partial” certificates (m SKi ) from other members. –member combines t certificates to get a GMC GMC = m SK1 m SK2 m SK3.. m SKt = m SK  Threshold signatures are NOT suitable in MANET and sensor networks. C urrently investigating Bilinear mappings [Admission Control in Peer-to-Peer: Design and Performance Evaluation, ACM SASN Workshop, October 2003.] [On the Utility of Distributed Cryptography in P2P and MANETs, ICNP 2003.]

Feature Summary RSAASMTS-RSATS-DSA Dealer involved  Simultaneous on-line presence  Accountability  Unlinkability  Verifiable Secret Share NA 

Some Results Signature generation Signature verification

(ID, PK) binding without a PKI Crypto-Generated Addresses (CGA) Statistically Unique Cryptographically Verifiable IDs [Montenegro, Castellucia] [O’Shea, Roe] = prefix | h( prefix | PK ) Secure Routing using CGA: AODV [Castellucia, Montenegro] DSR [Bobba, et al] PROs: no certificates, no PKI CONs: generation of bogus IDs New: CGA based on the small primes variation of the Feige-Fiat- Shamir (MFFS) [Statistically Unique and Cryptographically Verifiable Addresses: concepts and applications. ACM TISSEC, Feb. 2004] [Protecting AODV against impersonation attacks, ACM MC2R, October 2002]

Cooperation Enforcement in MANET Routing and Packet Forwarding cost energy. Selfish node saves energy for itself Without any incentive for cooperation network performance can be severely degraded. [Michiardi, Molva, EW’02]

Cooperation enforcement mechanisms Token-based [Yang,Meng,Lu] Nuglets [Buttyan,Hubaux] SPRITE [Zhong, Chen, Yang ] CONFIDANT [Buchegger,Le Boudec] CORE [Michiardi,Molva] Beta-Reputation [Josang,Ismail] Reputation-based Threshold cryptography Micro-payment

CORE a b c d E f g h Packet forwarding Source Node: g Destination Node: f Route: Reputation(b)  Reputation(d)  Reputation(E)  Packet forwarding Source Node: a Destination Node: f Route: Reputation(E) 

Cooperation Enforcement Evaluation with Game Theory Cooperative GT –Study the size (k) of a coalition of cooperating nodes –Nash Equilibrium  lower bound on k Non-cooperative GT –Utility function with pricing –Pricing used to guide the operating point (i.e. maximum of utility function) to a fair position –r i : dynamic reputation of node n i evaluated by her neighbors [Michiardi,Molva,CMS’02, WiOpt’03] [Srinivasan,et al.,INFOCOM’03]

Simulations: CORE – uniform traffic

Simulations: TFT – uniform traffic

Simulations: CORE – random traffic

Simulations: TFT – random traffic

Non-cooperative GT with pricing

Summary Specific requirements –Self organized bootstrapping of security associations –Cooperation enforcement Prospects –New tools from crypto bag of tricks (Id-based crypto,...) –Integrated mechanisms: reputation + key management Participation in MOBILEMAN project on Ad Hoc Networks ESAS st European Workshop on Security in Ad-Hoc and Sensor Networks. (5.-6. August, 2004)

ESORICS 2004 – RAID 2004 September Institut EURECOM Sophia Antipolis - FRANCE

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