Cryptanalysis and improvement of a certificateless signature scheme in the standard model

The first certificateless signature scheme provably secure in the standard model and an improved scheme were analyzed. A new malicious KGC attack called universal malicious KGC attack was given. In this attack, malicious KGC could generate the trapdoor system parameters of the schemes in set-up phase and forge signatures of any user for any message in the signing phase. An improved scheme was presented to defense this attack.