Cryptography in Heavily Constraint Environments

RuhrRuhrUniversityUniversityBochumBochum

Cryptography in Heavily Cryptography in Heavily

Constraint EnvironmentsConstraint Environments

Christof PaarChristof Paar

EUROBITS Center for IT SecurityEUROBITS Center for IT Security

COCOmmunication mmunication SSecuritecuritY Y (COSY) Group(COSY) Group

University of Bochum, GermanyUniversity of Bochum, Germany

www.crypto.rub.dewww.crypto.rub.de


Communication Security Communication Security (COSY) Group(COSY) Group

Workshop on Ad-Hoc Security 2002

ContentsContents

• Pervasive computing and embedded systems

• Pervasive computing and security• Constrained environments and crypto• Research problems




Characteristics of Traditional Characteristics of Traditional IT ApplicationsIT Applications

• Mostly based on interactive (= traditional) computers

• „One user – one computer“ paradigm• Static networks• Large number of users per network

Q: How will the IT future look?




Examples for Pervasive Examples for Pervasive ComputingComputing

• PDAs, 3G cell phones, ...• Living spaces will be stuffed with nodes• So will cars• Wearable computers (clothes, eye glasses, etc.)• Household appliances• Smart sensors in infrastructure (windows, roads,

bridges, etc.)• Smart bar codes (autoID)• “Smart Dust”• ...




Will that ever become Will that ever become reality??reality??

We don’t know, but: CPUs sold in 2000




Security and Economics of Security and Economics of Pervasive NetworksPervasive Networks

• „One-user many-nodes“ paradigm (e.g. 102-103 processors per human)

• Many new applications we don‘t know yet• Very high volume applications• Very cost sensitive• People won‘t be willing to pay for security

per se • People won‘t buy products without security




Where are the challenges for Where are the challenges for embedded security?embedded security?

• Designers worry about IT functionality, security is ignored or an afterthought

• Attacker has easy access to nodes • Security infrastructure (PKI etc.) is missing:

Protocols???• Side-channel and tamper attacks• Computation/memory/power constrained




Why do constraints matter?Why do constraints matter?

• Almost all ad-hoc protocols (even routing!) require crypto ops for every hop

• At least symmtric alg. are needed• Asymmetric alg. allow fancier protocols

Question: What type of crypto can we do?




Classification by Processor PowerClassification by Processor Power

Very rough classification of embedded processors

Class speed : high-end Intel

Class 0: few 1000 gates ?

Class 1: 8 bit P, 10MHz 1: 103

Class 2: 16 bit P, 50MHz 1: 102

Class 3: 32 bit P, 200MHz 1: 10




Case Study Class 0: RFIDCase Study Class 0: RFID

Recall: Class 0 = no P, few 1000 gates

• Goal: RFID as bar code replacement• Cost goal 5 cent (!)• allegedly 500 x 109 bar code scans worldwide per day

(!!)• AutoID tag: security “with 1000 gates” [CHES 02]

– Ell. curves (asymmetric alg.) need > 20,000 gates– DES (symmetric alg.) needs > 5,000 gates– Lightweight stream ciphers might work




Status Quo: Crypto for Class 1Status Quo: Crypto for Class 1

Recall: Class 1 = 8 bit P, 10MHz

Symmetric alg: possible at low data rates

Asymm.alg: very difficult without coprocessor






Symmetric alg: possible

Asymm.alg: possible if • carefully implemented, and • algorithms carefully selected (ECC feasible; RSA &

DL still hard)






Symmetric alg: possible

Asymm.alg: full range (ECC, RSA, DL) possible, some care needed for implementation




Open (Research) QuestionsOpen (Research) Questions

1. Symmetric algorithm for class 0 (e.g., 1000 gates) which are secure and well understood?

2. Alternative asymm. alg. for class 0 and class 1 (8 bit P) with 10x time-area improvement over ECC?

3. Are asymm. alg. which are “too short” (e.g., ECC with 100 bits) usable?

4. Ad-hoc protocols without long-term security needs?

5. Side-channel protection at very low costs?




Related Events at theRelated Events at theEUROBITS Center in BochumEUROBITS Center in Bochum

www.crypto.rub.de

1. Workshop on Side-Channel Attacks on Smart CardsJanuary 30-31, 2003

Cryptographic Hardware and Embedded SystemsCryptographic Hardware and Embedded Systems

September7-10

chesworkshop.org




Security Challenges: Many Security Challenges: Many Security Assumptions ChangeSecurity Assumptions Change

• No access to backbone: PKI does not work• New threats: sleep deprivation attack• Old threats (e.g., confidentiality) not always a

problem• Nodes have incentives to cheat in protocols • Security protocols ???




Our Research Our Research

Crypto algorithms in highly constrained environments

• Low-cost hardware for public-key algorithm• Ultra low-cost hardware for symmetric algorithms• Software for public-key, symmetric algorithms on

low-end processors Protocols for ad-hoc networks

• Secure communication in complex technical systems (airplanes, cars, etc.)

• Establishing trust in networks




Traditional Security Traditional Security ApplicationsApplications

Very often: computer & communication networks!

• (wireless) LAN / WLAN (Local Area Network)

• WAN (Wide Area Network)• PKI (Public Key Infrastructure)





(wireless) LAN / WLAN (Local Area Network)





WAN

(Wide Area Network)





PKI (Public Key Infrastructure)

enables secure LAN, WAN




Other Traditional Security Other Traditional Security ApplicationsApplications

• Antivirus• Firewalls• Biometrics




The IT FutureThe IT Future

• 2. Bridge sensors• 3. Cleaning robots• 6. Car with various IT services• 8. Networked robots• 9. Smart street lamps• 14. Pets with electronic

sensors• 15. Smart windows




Characteristics of Pervasive Characteristics of Pervasive Computing SystemsComputing Systems

• Embedded nodes (no traditional computers)• Connected through wireless, close-range

network (“Pervasive networks”)!• Ad-hoc networks: Dynamic addition and

deletion of nodes• Power/computation/memory constrained!• Vulnerable




Why Security in Pervasive Why Security in Pervasive Applications?Applications?

• Pervasive nature and high-volume of nodes increase risk potential (e.g., hacking into a car)

• Wireless channels are vulnerable (passive and active attacks)

• Privacy issues (geo-location, medical sensors, monitoring of home activities, etc.)

• Stealing of services (sensors etc.)

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Cryptography in Heavily Constraint Environments

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