Two password-authenticated key exchange protocol for three: safety analysis and improvement

Through security analysis to two existing verifier-based password-authenticated key exchange protocol for three,the fact that they are both insecure is pointed out,and a efficient two verifiers based password-authenticated key exchange protocol for three is put forward,which is based on the analysis.The protocol can make the both parties of communication produce four session keys in only two rounds without the inefficient public key algorithm,and the protocol is proved to have strong two-way authentication mechanism and the ability to resist various attack by security analysis.