Generic security-amplifying methods of ordinary digital signatures

Digital signatures are one of the most fundamental primitives in cryptography. In this paper, three new paradigms are proposed to obtain signatures that are secure against existential forgery under adaptively chosen message attacks (fully-secure, in short), from any weakly-secure signature. These transformations are generic, simple, and provably secure in the standard model. In the first paradigm, based on a weakly-secure signature scheme, the construction of a fully-secure signature scheme requires one-time signature additionally. However, the other two are built only on weakly-secure signatures. To the best of our knowledge, it is observed for the first time in this paper that two weakly-secure signature schemes are sufficient to construct a fully-secure signature scheme. Based on the new proposed paradigms, several efficient instantiations without random oracles are also presented. We also show that these fully-secure signature schemes have many special interesting properties in application.