CRYPTO '93 Proceedings of the 13th annual international cryptology conference on Advances in cryptology
Conditionally secure secret sharing schemes with disenrollment capability
CCS '94 Proceedings of the 2nd ACM Conference on Computer and communications security
Fully dynamic secret sharing schemes
Theoretical Computer Science
Communications of the ACM
Changing Thresholds in the Absence of Secure Channels
ACISP '99 Proceedings of the 4th Australasian Conference on Information Security and Privacy
Efficient and Unconditionally Secure Verifiable Threshold Changeable Scheme
ACISP '01 Proceedings of the 6th Australasian Conference on Information Security and Privacy
Threshold Schemes with Disenrollment
CRYPTO '92 Proceedings of the 12th Annual International Cryptology Conference on Advances in Cryptology
Key Escrow in Mutually Mistrusting Domains
Proceedings of the International Workshop on Security Protocols
Foundations of Cryptography: Volume 2, Basic Applications
Foundations of Cryptography: Volume 2, Basic Applications
Verifiable secret sharing and achieving simultaneity in the presence of faults
SFCS '85 Proceedings of the 26th Annual Symposium on Foundations of Computer Science
Updating the parameters of a threshold scheme by minimal broadcast
IEEE Transactions on Information Theory
Lattice-Based Threshold Changeability for Standard Shamir Secret-Sharing Schemes
IEEE Transactions on Information Theory
On Secret Reconstruction in Secret Sharing Schemes
IEEE Transactions on Information Theory
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This paper studies the methods for changing thresholds in the absence of secure channels after the setup of threshold secret sharing schemes. First, we construct a perfect (t,n) threshold scheme that is threshold changeable to t^'t, which is optimal with respect to the share size. This improves the scheme of Wang and Wong by relaxing the requirement from q=n+v to qn with the secret-domain F"q^v. But these threshold changeable schemes along with most previously known schemes turn out to be insecure under the collusion attack of players holding initial shares. By adding a broadcast enforcement term we enhance the model with collusion security and N options of threshold change. Then we construct a computationally secure scheme under the enhanced model, which involves much shorter shares and broadcast messages than the perfect schemes. Finally, we discuss how to realize the enrollment and disenrollment of players, and particularly, how to deal with L-fold changes of access polices.