Improved Signature Schemes for Secure Multi-Party Computation with Certified Inputs

The motivation for this work comes from the need to strengthen security of secure multi-party protocols with the ability to guarantee that the participants provide their truthful inputs in the computation. This is outside the traditional security models even in the presence of malicious participants, but input manipulation can often lead to privacy and result correctness violations. Thus, in this work we treat the problem of combining secure multi-party computation (SMC) techniques based on secret sharing with signatures to enforce input correctness in the form of certification. We modify two currently available signature schemes to achieve private verification and efficiency of batch verification and show how to integrate them with two prominent SMC protocols

An Enhanced Threshold RSA-Based Aggregate Signature Scheme to Reduce Blockchain Size

The transformative potential of blockchain technology has resulted in its widespread adoption, bringing about numerous advantages such as enhanced data integrity, transparency, and decentralization. Blockchain has effectively proven its ability to establish trustworthy systems across a multitude of applications. As the number of transactions recorded into a blockchain grows, the blockchain's size expands significantly, posing challenges to the network, particularly in terms of storage capacity and processing power. To address this problem, we present a cryptosystem based on RSA to provide aggregate signatures in blockchains. The aggregate signature replaces all transaction signatures of a block. In this scheme, all participating blockchain nodes use the same modulus $N$ , each with its own private and public key pair generated from $N$. Regardless of the number of transactions, nodes, and signers, the aggregate signature size is always $O(k)$ , where $k$ is a security parameter. The miner that constructs a candidate block computes the aggregate signature $\sigma$ , replaces all transaction signatures by $\sigma$ , and transmits the block with only one aggregate signature. The proposed scheme incorporates a flexible and accountable subgroup aggregate signature mechanism, allowing any subset $t$ of $n$ total elements to sign data, where $t$ is the required number of signers. To verify that a set of elements signed the block, the verifier requires the aggregate signature, the aggregate public key, and the data hash. This approach requires minimal interaction between the signers, which results in reduced network traffic. Regardless of the network size, there are always $t + n$ exchanged messages. Experimental analysis shows the proposed aggregate signature scheme's effectiveness in increasing security robustness and reducing block size and overall network traffic