In the era of growing threats posed by the development of quantum computers, ensuring the security of electronic services has become fundamental. The ongoing standardization process led by the National Institute of Standards and Technology (NIST) emphasizes the necessity for quantum-resistant security measures. However, the implementation of Post-Quantum Cryptographic (PQC) schemes, including advanced schemes such as threshold signatures, faces challenges due to their large key sizes and high computational complexity, particularly on constrained devices. This paper introduces two microcontroller-tailored optimization approaches, focusing on enhancing the DS2 threshold signature scheme. These optimizations aim to reduce memory consumption while maintaining security strength, specifically enabling the implementation of DS2 on microcontrollers with only 192 KB of RAM. Experimental results and security analysis demonstrate the efficacy and practicality of our solution, facilitating the deployment of DS2 threshold signatures on resource-constrained microcontrollers.

Privacy is a notoriously difficult property to achieve in complicated systems and especially in electronic voting schemes. Moreover, electronic voting schemes is a class of systems that require very high assurance. The literature contains a number of ballot privacy definitions along with security proofs for common systems. Some machine-checked security proofs have also appeared. We define a new ballot privacy notion that captures a larger class of voting schemes. This notion improves on the state of the art by taking into account that verification in many schemes will happen or must happen after the tally has been published, not before as in previous definitions. As a case study we give a machine-checked proof of privacy for Selene, which is a remote electronic voting scheme which offers an attractive mix of security properties and usability. Prior to our work, the computational privacy of Selene has never been formally verified. Finally, we also prove that MiniVoting and Belenios satisfies our definition.

Privacy is a notoriously difficult property to achieve in complicated systems and especially in electronic voting schemes. Moreover, electronic voting schemes is a class of systems that require very high assurance. The literature contains a number of ballot privacy definitions along with security proofs for common systems. Some machine-checked security proofs have also appeared. We define a new ballot privacy notion that captures a larger class of voting schemes. This notion improves on the state of the art by taking into account that verification in many schemes will happen or must happen after the tally has been published, not before as in previous definitions. As a case study we give a machine-checked proof of privacy for Selene, which is a remote electronic voting scheme which offers an attractive mix of security properties and usability. Prior to our work, the computational privacy of Selene has never been formally verified. Finally, we also prove that MiniVoting and Belenios satisfies our definition.

Introduced in 1996, NTRUEncrypt is not only one of the earliest but also one of the most scrutinized lattice-based cryptosystems and expected to remain secure in the upcoming era of quantum computing. Furthermore, NTRUEncrypt offers some efficiency benefits over “pre-quantum” cryptosystems like RSA or ECC since the low-level arithmetic operations are less computation-intensive and, thus, more suitable for constrained devices. In this paper we present Avrntru, a highly-optimized implementation of NTRUEncrypt for 8-bit AVR microcontrollers that we developed from scratch to reach high performance and resistance to timing attacks. Avrntru complies with the EESS #1 v3.1 specification and supports product-form parameter sets such as ees443ep1, ees587ep1, and ees743ep1. An entire encryption (including mask generation and blinding-polynomial generation) using the ees443ep1 parameters requires 847973 clock cycles on an ATmega1281 microcontroller; the decryption is more costly and has an execution time of 1051871 cycles. We achieved these results with the help of a novel hybrid technique for multiplication in a truncated polynomial ring, whereby one of the operands is a sparse ternary polynomial in product form and the other an arbitrary element of the ring. A constant-time multiplication in the ring given by the ees443ep1 parameters takes only 192577 cycles, which sets a new speed record for the arithmetic part of a lattice-based cryptosystem on AVR.

Internet voting can afford more inclusive and inexpensive elections. The flip side is that the integrity of the election can be compromised by adversarial attacks and malfunctioning voting infrastructure. Individual verifiability aims to protect against such risks by letting voters verify that their votes are correctly registered in the electronic ballot box. Therefore, voters need to carry out additional tasks making human factors crucial for security. In this article, we establish a categorization of individually verifiable Internet voting schemes based on voter interactions. For each category in our proposed categorization, we evaluate a voting scheme in a user study with a total of 100 participants. In our study, we assessed usability, user experience, trust, and further qualitative data to gain deeper insights into voting schemes. Based on our results, we conclude with recommendations for developers and policymakers to inform the choices and design of individually verifiable Internet voting schemes.

In e-voting protocols, cryptographers must balance usability with strong security guarantees, such as privacy and verifiability. In traditional e-voting protocols, privacy is often provided by a trusted authority that learns the votes and computes the tally. Some protocols replace the trusted authority by a set of authorities, and privacy is guaranteed if less than a threshold number of authorities are corrupt. For verifiability, stronger security is demanded. Typically, corrupt authorities that try to fake the tally result must always be detected.To provide verifiability, many e-voting protocols use Non-Interactive Zero-Knowledge proofs (NIZK). Thanks to their non-interactive nature, NIZK allow anybody, including third parties that do not participate in the protocol, to verify the correctness of the tally. Therefore, NIZK can be used to obtain universal verifiability. Additionally, NIZK also improve usability because they allow voters to cast a vote non-interactively.The disadvantage of NIZK is that their security is based on setup assumptions such as the common reference string (CRS) or the random oracle model. The former requires a trusted party to generate a CRS. The latter, though a popular model for secure protocol design, has been shown to be unsound.We address the design of e-voting protocols that provide verifiability without any trust assumptions. We show that Non-Interactive Witness-Indistinguishable proofs can be used for this purpose. Our e-voting protocols are private under the Decision Linear assumption, while perfect individual verifiability, i.e. a fake tally is detected with probability 1, holds unconditionally. Perfect universal verifiability requires a trusted public bulletin board. We remark that our definition of verifiability does not consider eligibility or end-to-end verifiability. First, we present a general construction that supports any tally function. Then, we show how to efficiently instantiate it for specific types of elections through Groth-Sahai proofs.

An unsolved debate in the field of usable security concerns whether security mechanisms should be visible, or black-boxed away from the user for the sake of usability. However, tying this question to pragmatic usability factors only might be simplistic. This study aims at researching the impact of displaying security mechanisms on User Experience (UX) in the context of e-voting. Two versions of an e-voting application were designed and tested using a between-group experimental protocol (N=38). Version D displayed security mechanisms, while version ND did not reveal any security-related information. We collected data on UX using stan-dardised evaluation scales and semi-structured interviews. Version D performed better overall in terms of UX and need fulfilment. Qualitative analysis of the interviews gives further insights into factors impacting perceived security. Our study adds to existing research suggesting a conceptual shift from usability to UX and discusses implications for designing and evaluating secure systems.

Du-Vote is a recently presented remote electronic voting scheme. Its goal is to be malware tolerant, i.e. provide security even in the case where the platform used for voting has been compromised by dedicated malware. For this it uses an additional hardware token, similar to tokens distributed in the context of online banking. The token is software closed and does not have any communication means other than a numerical keyboard and a small display. Du-Vote aims at providing vote privacy as long as either the vote platform or the vote server is honest. For verifiability, the security guarantees are aimed higher, indeed even if the token's software has been changed, and the platform and the server are colluding, attempts to change the election outcome should be detected with high probability. In this paper we provide an extensive security analysis of Du-Vote and show several attacks on both privacy as well as verifiability. We also propose changes to the system that would avoid many of these attacks.