Cryptanalysis of Two Proxy Signature Schemes
Shi Li Liang · Journal of Xiamen University · 2013
Attacks on Fu et al′s improved proxy signature and proxy aggregate signature schemes for mobile communication were presented.By constructing equivalent proxy secret keys,the original signer can easily forge valid proxy signature and proxy aggregate signature.It means that Fu et al′s method of adding random numbers is invalid.Security analysis show that Fu et al′s proxy signature and proxy aggregate signature schemes do not satisfy strong unforgeability.So they are insecure proxy signature schemes and can not be used in mobile communication.