A Modification of Jarecki and Saxena Proactive RSA Signature Scheme

Luo and Lu proposed URSA proactive signature scheme, the core of which is based on a new threshold signature protocol - the so-called t-bounded offsetting algorithm. Jarecki et al. have shown that the t-bounded offsetting algorithm leaks information for the shared secret which can be extended to a key-recovery attack on the URSA proactive signature scheme. Jarecki and Saxena proposed a fix to the scheme of Luo and Lu, turning it to a provably secure proactive RSA signature scheme. The authors also posed two open questions on the proactive RSA signature schemes. In this paper we give a solution to the second open problem posed by Jarecki and Saxena. Namely, we propose a proactive RSA signature scheme which does not require all participants to be active in the signature generation protocol.