Institute of Mathematics and Informatics Bulgarian Academy of Sciences
Serdica Journal of Computing, Vol. 1, No 3, (2007), 337p-364p
This paper investigates the security of Proactive Secret Sharing
Schemes. We first consider the approach of using commitment to 0 in the
renewal phase in order to refresh the player's shares and we present two types
of attacks in the information theoretic case. Then we prove the conditions
for the security of such a proactive scheme. Proactivity can be added also
using re-sharing instead of commitment to 0. We investigate this alternative
approach too and describe two protocols. We also show that both techniques
are not secure against a mobile adversary.
To summarize we generalize the existing threshold protocols to protocols
for general access structure. Besides this, we propose attacks against the
existing proactive verifiable secret sharing schemes, and give modifications
of the schemes that resist these attacks.
The paper has been presented at the International Conference Pioneers of Bulgarian
Mathematics, Dedicated to Nikola Obreshkoff and Lubomir Tschakaloff , Sofia, July, 2006.
The material in this paper was presented in part at the 11th Workshop on Selected Areas in Cryptography (SAC) 2004