Server-assisted signature with forward-security for mobile user

Digital signatures play a more and more important role in modern electronic commerce. Using a digital signature, a user can prove whether an electronic document is signed by him (her) or not. In this paper, we propose a server-assisted signature with forward-security for mobile user. In this model, a mobile user can produce a signature for his (her) company with the help of some servers. The system has forward secure property, that is, the secret shares are updated in each time period and the old secret shares can´t be computed from the new secret shares. It means that the attacker cannot forge the signatures of previous periods even if all the current shares are compromised. Finally, we prove the proposed signature is correct and forward secure.