Generic Security-Amplifying Methods of Ordinary Digital Signatures

摘要

We describe two new paradigms on how to obtain ordinary signatures that are secure against existential forgery under adaptively chosen message attacks (fully-secure, in short), from any signatures satisfy only a weak security notion called existentially unforgeable against weak chosen message attacks (weakly-secure, in short). The new transformations from a weakly-secure signature scheme to fully-secure signature scheme are generic, simple, and provably secure in the standard model. Moreover, these two new paradigms are built only on weakly-secure signatures. They are different from the previous methods, which also relied on some other cryptographic protocols or non-standard models. By using two new paradigms, several efficient instantiations without random oracles are also presented, which are based on two previous weakly-secure signature schemes. These fully-secure signature schemes have many special interesting properties compared with the previous related signature schemes.