Improved anonymity preserving three-party mutual authentication key exchange protocol based on chaotic maps.

Three-party authentication key exchange is a protocol that allows two users to set up a session key for encrypted communication by the help of a trusted remote server. Providing user anonymity and mutual authentication in the authentication key exchange is important security requirements to protect users' privacy and enhance its security performance. Recently Li proposed a chaotic maps-based authentication key exchange protocol which attempts to provide mutual authentication and user anonymity, but we found that there were some faults in the key exchange phase and password change phase of his scheme. We prove that Li's scheme does not provide user anonymity and that the user's privacy information is disclosed, and propose enhanced three-party authentication key exchange protocol that provides user anonymity and we analyse its security properties and verify its validity based on BAN logic and AVISPA tool.

Cryptanalysis and improved mutual authentication key agreement protocol using pseudo-identity.

The authentication key agreement is a scheme that generates a session key for encrypted communication between two participants. In the authentication key agreement, to provide the mutual authentication and the robust session key agreement is one of the important security requirements to enhance the security performance of key agreement. Recently Zhou et al. had proposed the key agreement protocol using pseudo-identifiers, but we found that there were weaknesses in their protocol. We have demonstrated that Zhou et al.'s protocol is vulnerable to replay attack, fails to provide mutual authentication, no key control, re-registration with the original identifier and efficiency in the verification of wrong password. We improved their scheme and proposed an improved authentication key agreement protocol that provides robust mutual authentication and the secure session key agreement. We analyzed its security performance using BAN logic and AVISPA tools and compared computational cost, communication overhead and security properties with other related schemes.

Novel exchangeable effector loci associated with the Pseudomonas syringae hrp pathogenicity island: evidence for integron-like assembly from transposed gene cassettes.

Pseudomonas syringae strains use a type III secretion system (TTSS) to translocate effector proteins that assist in the parasitism of host plant cells. Some genes for effector proteins are clustered in the exchangeable effector locus (EEL) associated with the hrp pathogenicity island. A polymerase chain reaction-based screen was developed to amplify the EEL from P. syringae strains. Of the 86 strains screened, the EEL was successfully amplified from 30 predominately North American P. syringae pv. syringae strains using hrpK and queA-derived primers and from an additional three strains using hrpL and queA-derived primers. Among the amplified EEL, ten distinct types of EEL were identified that could be classified into six families distinguishable by genetic composition, but other types of EEL may be present in strains isolated in other geographical regions. No linkage with the host range of the source strain was apparent. Gene cassettes carrying conserved flanking, coding, and intergenic sequences, present in different combinations, were identified in the characterized EEL. Six new alleles of known effectors were identified that differed from the homolog in sequence, size, or both of the gene. One of these apparently novel effector proteins, HopPsyB, retained a strongly conserved amino terminus similar to that of HopPsyA, but other regions of the two polypeptides were only weakly similar. hopPsyB was expressed from an apparent operon that included hrpK and a shcA homolog, shcB. Escherichia coli MC4100 expressing the hrp TTSS, ShcB, and HopPsyB elicited the hypersensitive response (HR) in tobacco, consistent with effector production. Indicative of translocation as an effector, P. syringae pv. tomato DC3000 expressing a HopPsyB':'AvrRpt2 fusion elicited the HR in RPS2+ Arabidopsis thaliana. P. syringae pv. tomato DC3000 carrying HopPsyB exhibited slightly enhanced virulence in several Brassica spp. These results are consistent with the hypotheses that the EEL is a source of disparate effectors functioning in pathogenicity of P. syringae strains and that it evolved independently of the hrp pathogenicity island central conserved region, most likely through integron-like assembly of transposed gene cassettes.