2 research outputs found
Efficient Cloud-based Secret Shuffling via Homomorphic Encryption
When working with joint collections of confidential data from multiple
sources, e.g., in cloud-based multi-party computation scenarios, the ownership
relation between data providers and their inputs itself is confidential
information. Protecting data providers' privacy desires a function for secretly
shuffling the data collection. We present the first efficient secure
multi-party computation protocol for secret shuffling in scenarios with a
central server. Based on a novel approach to random index distribution, our
solution enables the randomization of the order of a sequence of encrypted data
such that no observer can map between elements of the original sequence and the
shuffled sequence with probability better than guessing. It allows for
shuffling data encrypted under an additively homomorphic cryptosystem with
constant round complexity and linear computational complexity. Being a
general-purpose protocol, it is of relevance for a variety of practical use
cases
Compact Zero-Knowledge Proofs of Small Hamming Weight
We introduce a new technique that allows to give a zero-knowledge proof that a committed vector has Hamming weight bounded by a given constant. The proof has unconditional soundness and is very compact: It has size independent of the length of the committed string, and for large fields, it has size corresponding to a constant number of commitments. We show five applications of the technique that play on a common theme, namely that our proof allows us to get malicious security at small overhead compared to semi-honest security: 1) actively secure k-out-of-n OT from black-box use of 1-out-of-2 OT, 2) separable accountable ring signatures, 3) more efficient preprocessing for the TinyTable secure two-party computation protocol, 4) mixing with public verifiability, and 5) PIR with security against a malicious client