Improvement of hwang lo lin scheme based on an id based cryptosystem
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Improvement of Hwang-Lo-Lin scheme based on an ID-based cryptosystem. No author given (Korea information security Agency) Presented by J.Liu. Outline. Introduction Review of the Hwang-Lo-Lin scheme Cryptanalysis The modified ID-based identification scheme Security analysis

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Improvement of Hwang-Lo-Lin scheme based on an ID-based cryptosystem

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Improvement of hwang lo lin scheme based on an id based cryptosystem

Improvement of Hwang-Lo-Lin scheme based on an ID-based cryptosystem

No author given

(Korea information security Agency)

Presented by J.Liu


Outline

Outline

  • Introduction

  • Review of the Hwang-Lo-Lin scheme

  • Cryptanalysis

  • The modified ID-based identification scheme

  • Security analysis

  • Performance analysis

  • Conclusions


Introduction

Introduction

  • ID-based public key cryptosystem.

  • Maurer-Yacobi(1996)Tseng-Jan(1998)

    Hwang-Lo-Lin(2004)Horng-Liu-Liu(2005)  This Letter(2005)

  • Hwang et al. developed the improved scheme was suitable for the wireless environment.


Review of the hwang lo lin scheme

Review of the Hwang-Lo-Lin scheme

  • TA setup the system parameters as following:

    • N = p1p2 p3p4, where pi are primes and their decimal digits are between 60-70, (pi-1)/2 are odd and pair wise relatively prime.

    • DLP is feasible but factoring N is infeasible.

    • g is a primitive root in each GF(pi).

    • h(.) is an one way hash function.

    • ed = 1 mod (N) and tv = 1 mod (N).


Improvement of hwang lo lin scheme based on an id based cryptosystem

Cont

  • IDb, IDm: identity of base station(BS) and mobile device(M), respectively.

  • sb = et  logg(IDb2) mod (N) is secret key for BS.

  • sm = et  logg(IDm2) mod (N) is secret key for M.

  • T: timestamp

    {N, g, e, h(.)}are public parameters and keep {p1, p2 , p3, p4 , t, v, d } secret.


Login and authentication

Login and authentication

  • Choose kR ZN*, computes Y = (IDm2)k mod N , Z = (IDb2)ksmT mod N

  • Sends {IDm, Y, Z, T } to BS.

  • BS computes Z’ = (Y)sbT, checks Z = Z’

    If yes then… else….

?


Key points

Key points


Cryptanalysis

Cryptanalysis

  • Attacker forge {IDm, Y1, Z1, T’ } from a valid login message {IDm, Y, Z, T } by Y1 = YrT mod N and Z1 = ZrT’ mod N.


The modified id based identification scheme

The modified ID-based identification scheme

  • The parameters are the same of Hwang’s scheme, but the 4 primes have bit size more than 1024 bits. (DLP OK? about 300 decimal digits)

  • M sends {IDm, Z, T} to BS, where Z = H((IDb2)smT mod N)

  • BS verifies by Z = H((IDm2)sbT mod N)


Security analysis

Security analysis

  • Passive replay attack: Changes timestamp T.H((IDm2)sbT mod N) H((IDm2)sbT’ mod N)

  • Active replay attack: The attacker can not change Z and T without sm and sb.

  • ID-stolen attack: The same with 2.


Performance analysis

Performance analysis

  • Without random number generator(hash function).

  • Shorter message length (1/2).

  • Fewer exponential operation (21).

  • More suitable in wireless environment.


Conclusion

Conclusion

  • Secure

  • More suitable.


  • Login