COMP4337/9337: Securing Fixed and Wireless Networks
WK-08: Security in Wireless Broadcast
Professor Sanjay K. Jha
School of Computer Science and Engineering, UNSW
Copyright By PowCoder代写 加微信 powcoder
• QuickoverviewofEllipticCurveDeffie-Hellman (ECDH) and Datagram TLS as lightweight solution for many wireless (IoT) solutions.
• SecurityChallengesinwirelessbroadcast
• Advancedtechniquesusinghash-chains,
• ApplicationcasestudyofCodedisseminationin a multi-hop wireless network
Datagram TLS (DTLS)
• SSL Designed to run on top of TCP
• Datagram TLS developed later to run over connectionless UDP
– RFC 4347 for details
• Already supported by several implementations
• Very similar to TLS
– Needs extra control messages as UDP doesn’t provide these like TCP
– Sequence number in record header to protect from Replay attack
• If very lossy network, may have issues with lot of restranmissons for reliability
Elliptic Curve (ECC) Scheme
• Key Agreement, aka, Elliptic Curve Deffie-Hellman (ECDH)
oAllows for establishment of shared secret similar to DH
oThe shared key is then used for symmetric encryption or for further session/temporal key derivation
• Digital Signature: Elliptic Curve Digital Signature Algorithm (ECDSA), allows use of public/private key for signing a message and verification of signature, more efficient than RSA based DSA.
Elliptic Curve Cryptography
Elliptic curve cryptography (ECC) is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite field.
ECC presents various benefits over RSA such as: – fastcomputation
– smallkeysize
– compactsignatures.
For example, to provide equivalent security to 1024-bit RSA, an ECC scheme only needs 160 bits.
Elliptic Curve Diffie- Exchange
1. Alice and Bob publicly agree on an elliptic curve E over a finite field Zp.
2. Next Alice and Bob choose a public base point B on the elliptic curve E.
3. Alice chooses a random integer 1
– Need time synchronization
– Not perfectly robust to packet loss
Learning Outcomes
• AppreciatehowBroadcast/multicastfundamentally changes protocol design space for authentication.
• Understandtradeoffbetweenreliabilityandsecurity – Key exchange etc must be reliable?
• UnderstandhashchainandMerkletreealgorithms and their application for security.
• Understand various threats in adhoc, wireless sensor networks and IoT
• Appreciatethatdifferentpointsofthedesignspace have different “best solution”
MERKLE TREE
– Appendix-A, L. Buttyan and J. P. Hubaux, Security and Cooperation in Wireless Networks
– A. Perrig, R. Canetti, D. Song, and J. D. Tygar. Efficient and secure source authentication for multicast. In Proceedings of the Sympo- sium on Network and Distributed Systems Secu- rity (NDSS 2001), pages 35–46. Internet Society, February 2001
Seluge/Deluge
– , , An Liu, and Wenliang Du. Seluge: Secure and dos- resistant code dissemination in wireless sensor networks. In IPSN ’08: Proceedings of the 7th international conference on Information processing in sensor networks, pages 445–456, 2008.
A good paper on Broadcast Encryption scheme
– D. Boneh, C. Gentry, and B. Waters. Collusion resistant broadcast encryption with short ciphertexts and private keys. In Advances in Cryptology–CRYPTO 2005, pages 258–275, 2005.
Reference List
Reference (Contd)
• NaCL (Salt) Network and Cryptography Library (http://nacl.cr.yp.to )
• RFC 4347 – Datagram Transport Layer Security
• For interactive ECC curve etc
– https://www.certicom.com/ecc_tutorial/ecc_javaCurve.html
– ECC Video ( Search for Elliptic Curve Addition)
• ACKNOWLEDGMENT: Foils contributed by Phd students Hailun Tan, Young
– Some adapted from Prof Adrian Perrig.
– ECC foils are modified from ’s version.
• Optional Read:
– Shamir, Adi (1979), “How to share a secret”, Communications of the ACM, 22 (11): 612–613,.
– R. Canetti, J. Garay, G. Itkis, D. Micciancio, M. Naor, and B. Pinkas. Multicast security: A taxonomy and some efficient constructions. In INFOCOMM’99, pages 708–716, March 1999.
private key public key
unsecure channel
private key
huge prime number
shared secret
Diffie-Hellman key exchange
Alice’s private key = 5, Bob’s private key = 4, g=3, p=7 Alice’spublickey=35 mod7=5,Bob’spublickey=34 mod7=4 Alice’ssharedkey=45 mod7=2,Bob’ssharedkey=54 mod7=2
Examples of Elliptic Curves (Optional)
• y2 = x3-7x+6 • y2 = x3-2x+4
-3 -2 -1 -2
-1 -2 -3 -4
Adding Two Points (Geometrically): xP 1 xQ
• We skip maths/algebraic details (beyond scope)
• The line L through P and Q will intersect the curve at one other point.
• Call this third point -R.
• Reflect the point -R about the x-axis to point R.
• y2 = x3-7x+6
Point Doubling: xP=xQ and yP = yQ
• Since P = Q, the line L through P and Q is tangent to the curve at P.
• Again L will intersect the curve at another point, -R.
• As in Case 1, reflect -R about the x-axis to point R.
• Notation: 2P = P+P
• Basically this computation (and variants) is more efficient than the standard Diffie-Hellman
• Crypto: Let P and Q be two points on an elliptic curve such that kP = Q, where k is a scalar. Given P and Q, it is hard to compute k.
• y = x -7x+6
程序代写 CS代考 加微信: powcoder QQ: 1823890830 Email: powcoder@163.com