Wednesday, February 20, 2019 - 12:00pm to 1:00pm
Location:8102 Gates Hillman Centers
Speaker:VIPUL GOYAL, Associate Professor https://www.cs.cmu.edu/~goyal/
Secret sharing is typically concerned with hiding the secret. However, what if the goal of the adversary is to tamper with the secret instead? In this work, we initiate a systematic study of what we call non-malleable secret sharing. Very roughly, the guarantee we seek is the following: the adversary may potentially tamper with all of the shares, and still, either the reconstruction procedure outputs the original secret, or, the original secret is ''destroyed'' and the reconstruction outputs a string which is completely ''unrelated'' to the original secret. This notion is inspired by the beautiful line of works on non-malleable codes.
We will present a construction of a t-out-of-n non-malleable secret sharing scheme against an adversary who arbitrarily tampers each of the shares independently. Going further, we also present t-out-of-n non-malleable secret sharing scheme in a stronger adversarial model where an adversary may jointly tamper multiple shares. Our constructions are unconditional and the adversary is allowed to jointly-tamper subsets of up to (t-1) shares. No cryptography is used.