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Threshold password authentication against guessing attacks in Ad hoc networks

This paper discusses a novel threshold password authentication scheme designed to resist guessing attacks in ad hoc networks. It emphasizes the importance of user-defined passwords that are stored securely, allowing users to change passwords freely without administrative knowledge. The proposed method utilizes Shamir’s secret sharing and ensures mutual authentication while maintaining service availability, even if several server nodes fail. This system addresses security threats, including replay and modification attacks, while minimizing risks associated with lost mobile devices.

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Threshold password authentication against guessing attacks in Ad hoc networks

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  1. Threshold password authentication against guessing attacks in Ad hoc networks Chai, Zhenchuan; Cao, Zhenfu; Lu, Rongxing Ad Hoc Networks Volume: 5, Issue: 7, September, 2007, pp. 1046-1054 97/09/24H.-H. Ou

  2. Introduction • Password Authentication • Password or Verification Table • Secret Share • Smart Card • Threshold Password Authentication Scheme • (t, n) threshold password authentication H.-H. Ou

  3. Requirements • The password or verification tables are not stored inside the server nodes. • The password can be chosen and changed freely by the owner. • The password cannot be revealed by the administrator of the server. • The length of a password must be appropriate for memorization. • The scheme can achieve mutual authentication • The system secret cannot be leaked even if some of the server nodes are compromised. • The availability of the system should not be affected even if some of the server nodes are unavailable. • No one can impersonate a legal user to login the server. • The scheme must resist the replay attack, modification attack and stolen-verifier. • The password cannot be broken by guessing attacks even if the mobile device is lost. H.-H. Ou

  4. Basic concepts of the proposed • Hard problem assumptions • Hardness of inverting an one-way hash function • Hardness of discrete logarithm program • Hardness of computational Diffie-Hellman problem • Shamir’s secret sharing scheme • (t,n) secret sharing scheme • Select a large prime p(>x), and a random polynomial f(.) over Zp of degree t-1, satisfying f(0) = x. • Give xi = f(i) to Si, I = 1,…,n • When t servers cooperate, x = f(0) = , where is the Lagrange coefficients. H.-H. Ou

  5. Notations H.-H. Ou

  6. The proposed(1/3) • Set up process • Select a random polynomial f(.) over Zq of degree t-1, satisfying f(0)=x. • Compute f(i)=xi, then send xi to Si through a secure channel • Discard x • Registration phase Communication server H.-H. Ou

  7. The proposed(2/3) • Login & authentication phase Communication server = h(ID)x = h(ID)rxi H.-H. Ou

  8. The proposed(3/3) • Changing password • User can changed freely without registration again. (?) • Smart confirm the validity of PW by interacting with ζ • Replace βwithβ-h(PW)+h(PW*) mod p H.-H. Ou

  9. Discussion • No password or verification table • Users could choose their own passwords, and can change their passwords without registration again. • Allows user to choose a short and memorable password, without worrying about subjecting to guessing attacks. • Administrator of server cannot know the password of the user. • Achieves mutual authentication • Even if an intruder break into up to t-1 server nodes, he cannot obtain any information about the system key x. • Even if n-t sever nodes are unavailable, the last t nodes can still provide service to user nodes. H.-H. Ou

  10. Performance • Liao-Lee-Hwang’s scheme • Designed for single client/server applications • Comparison with ten existing smart card based schemes and only the proposed can against offline guessing attacks. Liao-Lee-Hwang’s scheme ? H.-H. Ou

  11. comments • How to suitable the condition of Ad hoc networks? • The changing password process is must to contact with the ζ H.-H. Ou

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