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A Public Key Cryptographic Method for Denial of Service Mitigation in Wireless Sensor Networks. 20082065 Myunghan Yoo August 2, 2008. O. Arazi , H. Qi , D. Rose IEEE SECON 2007 proceedings. Progress. Problem & background Solution Discussion. Public Key Cryptography.
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A Public Key Cryptographic Method for Denial of Service Mitigation in Wireless Sensor Networks 20082065 MyunghanYoo August 2, 2008 O. Arazi, H. Qi, D. Rose IEEE SECON 2007 proceedings
Progress • Problem & background • Solution • Discussion
Public Key Cryptography • Use private and public keys • Given public key, easy to compute -> anyone can lock • Only those who has private key compute its inverse-> only those who has it can unlock, vice versa. Attacker C=E(P, Ke) P=D(C, Kd ) P P P C D E() D() Insecure channel Kd Ke Key Key
Usage of PKC (I) • For Privacy - Encrypt M with Bob’s public key : C = eK(Bp,M) - Decrypt C with Bob’s private key : D = dK(Bs,C) * Anybody can generate C, but only Bobcan recover C to M. C dk( , ) ek( , ) M M Public directory Alice : Ap Bob : Bp Chaum : Cp . . BS BP
Usage of PKC (II) • For authentication (Digital Signature) - Encrypt M with Alice’s private key : C = dK(As,M) - Decrypt C with Alice’s public key : D = eK(Ap,C) * Only Alice can generate C, but anybody can verify C. C M ek( , ) dk( , ) M Public directory Alice : Ap Bob : Bp Chaum : Cp . . As Ap
Motivation & Objective • Public Key Cryptography (PKC) • Denial-of-Service Attack in PKC • With repeated & meaningless requests to normal nodes to establish a session key, the adversary causes attacked normal nodes to waste energyresources
Objective & Key Idea • Objective • Mitigating Denial-of-Service (DoS) attacks • Key Idea • Loading heavy computational burden on the instigator
Progress • Problem & background • Solution • Discussion
Overview of Proposed Scheme Stage A: Alice proving her validity to Bob A relatively energy draining procedure on Alice’s part If successful Stage B: Bob proving her validity to Alice A relatively low energy draining procedure on Bob’s part If successful: both users hold an ephemeral shared secret key
The Instigator Proving Its Validity Alice Bob nA IDA CRA H(nA, IDA) = nAIDA CRA = [H(nA, IDA)]dca mod nCA (CRA)e mod nCA = H(nA, IDA) If so, generates a message, m, such that: t= me mod nA t tdA mod nA = m 512 bits or 1024 bits x: LSB of message m compares nA: Alice’s public key, IDA: Alice’s public key ID, CRA: Alice’s certificate signed by CA with its private key, e, nCA : CA’s public key
Message m z 212bits y 200bits x 100bits • x: Significant bits to identify the instigator • y and z: Factors of an ephemeral key Example of message m where the length of m is 512 bits.
Overview of Proposed Scheme Stage A: Alice proving her validity to Bob A relatively energy draining procedure on Alice’s part If successful Stage B: Bob proving her validity to Alice A relatively low energy draining procedure on Bob’s part If successful: both users hold an ephemeral shared secret key
The Approached Node Proving Its Validity • Key Transport • Elliptic Curve Digital Signature Algorithm (ECDSA) • Self-Certified DH Fixed Key-Generation
Key Transport Alice Bob Stage A If successful nB, CRB, IDB, SB Validation of the values: (CRB)e mod nCA = H(nB, IDB), (SB)e mod nB = y SB = ydB mod nB Stage B: If successful KAB-final = z
ECDSA Alice Bob Stage A V = u · G C is scalar of V L = u-1(y + dB · C) mod ordG If successful (C, L) Calculatesh = L-1,q1 = y · h mod ordG, q2 = C · h mod ordG, P = q1 · G + q2 · V, and C’ is scalar of P If C’ = C Stage B: KAB-final = z
Self-Certified DH Fixed Key-Generation Alice Bob Stage A If successful nB, CRB, IDB Self-Certified DH Fixed Key-Generation KAB-temp = KAB (generated by Alice) = nA x [H(IDB, nB) x nB + nCA] = KBA (generated by Bob) = nB x [H(IDA, NA) x nA + nCA] Stage B: KAB-final = H(KAB-temp, m’)
Implementation Results Using 1024-Bit RSA and 160-bit ECC on the Intel MOTE 2 Platform from 312 MHz core clock
Progress • Problem & background • Solution • Discussion
Contribution • This paper may be the first try of DoS attack mitigation for PKC
Discussion • Unclear environment of implementation • communication distance between Alice and Bob • Yet, unsuitable PKC in the WSN • Incoherent logic • Applying to only a suspicious node is needed • DoS attack with incomplete stage A
DoS attack with incomplete stage A Alice Bob nA IDA CRA H(nA, IDA) = nAIDA CRA = [H(nA, IDA)]dca mod nCA (CRA)e mod nCA = H(nA, IDA) If so, generates a message, m, such that: t= me mod nA Completed part t tdA mod nA = m Incompleted part 512 bits or 1024 bits x: LSB of message m compares nA: Alice’s public key, IDA: Alice’s public key ID, CRA: Alice’s certificate signed by CA with its private key, e, nCA : CA’s public key