Improvement of A proactive Threshold Signcryption Scheme
Feixiang Li, Chunxiang Xu, Shijie Zhou · International Journal of Computers and Applications · 2008
In 2005, Ma et al. proposed an efficient and proactive threshold signcryption scheme. They defined some security models with regard to the threshold signcryption versions of confidentiality, existential unforgeability and robustness. They claimed that their scheme is secure under these models. In this paper, we show that their scheme cannot achieve the claimed existential unforgeability by demonstrating an insider attack. We further propose an improved scheme that overcomes the weakness of the Ma et al.'s scheme.