Paper 2016/379

Two More Efficient Variants of the J-PAKE Protocol

Jean Lancrenon, Marjan Škrobot, and Qiang Tang


Recently, the password-authenticated key exchange protocol J-PAKE of Hao and Ryan (Workshop on Security Protocols 2008) was formally proven secure in the algebraic adversary model by Abdalla et al.(IEEE S&P 2015). In this paper, we propose and examine two variants of J-PAKE - which we call RO-J-PAKE and CRS-J-PAKE - that each makes the use of two less zero-knowledge proofs than the original protocol. We show that they are provably secure following a similar strategy to that of Abdalla et al. We also study their efficiency as compared to J-PAKE's, also taking into account how the groups are chosen. Namely, we treat the cases of subgroups of the finite fields and elliptic curves. Our work reveals that, for subgroups of finite fields, CRS-J-PAKE is indeed more efficient than J-PAKE, while RO-J-PAKE is much less efficient. On the other hand, when instantiated with elliptic curves, both RO-J-PAKE and CRS-J-PAKE are more efficient than J-PAKE, with CRS-J-PAKE being the best of the three. We illustrate this experimentally, making use of recent research by Brier et al. (CRYPTO 2010). Regardless of implementation, we note that RO-J-PAKE enjoys a looser security reduction than both J-PAKE and CRS-J-PAKE. CRS-J-PAKE has the tightest security proof, but relies on an additional trust assumption at setup time. We believe our results can be useful to anyone interested in implementing J-PAKE, as perhaps either of these two new protocols may also be options, depending on the deployment context.

Available format(s)
Cryptographic protocols
Publication info
Published elsewhere. Minor revision. ACNS 2016
Password-authenticated key exchangeJ-PAKEEfficiencyRandom oracleCommon reference stringZero-knowledge proof
Contact author(s)
marjan skrobot @ uni lu
2016-04-14: received
Short URL
Creative Commons Attribution


      author = {Jean Lancrenon and Marjan Škrobot and Qiang Tang},
      title = {Two More Efficient Variants of the J-PAKE Protocol},
      howpublished = {Cryptology ePrint Archive, Paper 2016/379},
      year = {2016},
      note = {\url{}},
      url = {}
Note: In order to protect the privacy of readers, does not use cookies or embedded third party content.