Informatica

This paper presents an improved method inspired by the recently proposed Pretty‐Simple PAKE (Password Authenticated Key‐Exchange) protocol, which is already a well‐known, robust and simple password authenticated key exchange scheme. In our even more efficient scheme, only the password needs to be negotiated in advance, and the computations have also been simplified. Our scheme is based on the elliptic curve discrete logarithm problem and can gain the benefit from the key block size, speed and security. Since our new scheme is both efficient and fast with a low cost for device storage, it is especially suitable for the wireless network environment.

Recently, Tseng et al. proposed an improvement on Peyravian and Zunic's protected password transmission scheme and protected changing scheme to remove some security flaws. However, as we will point out in this paper, any adversary can intercept the request for changing the password sent by a legal user and modify it with a wrong password. Furthermore, we shall also propose an improved version of their protected password changing scheme to help it out of the trouble.

In the generalized group‐oriented cryptosystem, the sender can send a conditional message to a group of users such that only the specified sets of users in this group can cooperate to decrypt this message. In this paper, we will use an ElGamal cryptosystem and an elliptic curve ElGamal cryptosystem to achieve the purposes of generalization and group‐orientation, respectively. Both of our schemes are more efficient than Tsai et al.'s scheme in terms of sender's computational complexity.