A multi-designated verifier signature (MDVS) is a digital signature that empowers a signer to designate specific verifiers capable of verifying signatures. Notably, designated verifiers are allowed to not only verify signatures but also simulate “fake” signatures indistinguishable from real ones produced by the original signer. Since this property is useful for realizing off-the-record (i.e., deniable) communication in group settings, MDVS is attracting attention in secure messaging. Recently, Damgård et al. (TCC'20) and Chakraborty et al. (EUROCRYPT'23) have introduced new MDVS schemes, allowing a subset of designated verifiers to simulate signatures in contrast to the conventional one, which requires all designated verifiers for signature simulation. They also define a stronger notion of security for them. This work delves into this new MDVS and offers a comprehensive formalization. We identify all possible security levels of MDVS schemes in subset simulations and prove that some of them are not feasible. Furthermore, we demonstrate that MDVS schemes meeting the security notion defined by Chakraborty et al. imply IND-CCA secure public-key encryption schemes. Beyond formalization, we present new constructions of MDVS schemes in subset simulation. Notably, we introduce a new construction of strongly secure MDVS schemes based on ring signatures and public-key encryption, accompanied by a generic conversion for achieving consistency through non-interactive zero-knowledge arguments. Finally, we evaluate the efficiency of our MDVS schemes in classical and post-quantum settings, showing their practicality.

Vulnerabilities in Ethereum smart contracts often cause significant financial damage. Whereas the Solidity compiler has been updated to mitigate vulnerabilities, the effectiveness of these updates remains undisclosed to the best of our knowledge. In this paper, we aim to shed light on the impact of compiler versions on reducing vulnerabilities in Ethereum smart contracts. To achieve this, we collected 497,344 contracts with Solidity source codes from the Ethereum blockchain and analyzed their vulnerabilities. For three vulnerabilities of high severity, i.e., Locked Money , Using tx.origin , and Unchecked Call , we illustrate their appearance rate changes, showing decreases attributed to major updates of the Solidity compiler. Subsequently, we found the following four key insights. Firstly, updates to version 0.6 and version 0.8 led to decreased appearance rates for Locked Money . Secondly, regardless of compiler updates, the appearance rate for Using tx.origin was significantly low. Thirdly, the appearance rate for Unchecked Call significantly decreased from version 0.5 to version 0.8. Lastly, as an incidental discovery from our empirical study, we identified implications for code clones, which merit attention from subsequent researchers and developers.