Kannan Karthik, Indian Institute of Technology - Guwahati, India

Threshold ramp secret sharing schemes are designed so that (i) certain subsets of shares have no information about the secret, (ii) some subsets have partial information about the secret and (iii) some subsets have complete information to recover the secret. However most of the ramp schemes in present literature do not control the leakage of information in partial access sets, due to which the information acquired by these sets is devoid of structure and not useful for fine-grained access control. Through a non-perfect secret sharing scheme called MIX-SPLIT, an encoding methodology for controlling the leakage in partial access sets is proposed and this is used for fine-grained access to binary strings. The ramp code generated using MIX-SPLIT requires a much smaller share size of O(n), as compared to Shamir's ramp adaptation which incurs a share size of atleast O(n2) for the same multi-access structure. The proposed ramp code is finally applied towards the protection and fine-grained access of industrial design drawings.

MIX-SPLIT, Ramp code, Non-perfect secret sharing, Fine-grained access control, Industrial designs