How to Store some Secrets

This paper introduces a special type of symmetric cryptosystem called multi-encryption scheme. It allows users to encrypt multiple plaintexts into a single ciphertext. Each plaintext is protected with its own secret key, meaning that they can be decrypted individually by applying the decryption function with the corresponding key to the ciphertext. Compared to encrypting the ciphertexts one-by-one using a standard symmetric cryptosystem, the main advantage of using a multi-encryption scheme is the no-search property, which guarantees that knowing the key is sufficient for decrypting a single plaintext. We show how to construct a multi-encryption scheme based on polynomials over finite fields. A possible application area is coercion-resistant electronic voting. To ensure a strong form of privacy, voters are equipped with multiple fake credentials, which are indistinguishable from the proper one. While theoretically sound, this requires a voter to perfectly recall multiple lengthy random numbers, and to know which of them is the proper one. To ensure 100\% recall, users need to manage these numbers and keep them secret. A multi-encryption scheme is an elegant solution for this problem

Enhancing Data Security by Making Data Disappear in a P2P Systems

This paper describes the problem of securing data by making it disappear after some time limit, making it impossible for it to be recovered by an unauthorized party. This method is in response to the need to keep the data secured and to protect the privacy of archived data on the servers, Cloud and Peer-to-Peer architectures. Due to the distributed nature of these architectures, it is impossible to destroy the data completely. So, we store the data by applying encryption and then manage the key, which is easier to do as the key is small and it can be hidden in the DHT (Distributed hash table). Even if the keys in the DHT and the encrypted data were compromised, the data would still be secure. This paper describes existing solutions, points to their limitations and suggests improvements with a new secure architecture. We evaluated and executed this architecture on the Java platform and proved that it is more secure than other architectures.Comment: 18 page

ZETA - Zero-Trust Authentication: Relying on Innate Human Ability, not Technology

Reliable authentication requires the devices and channels involved in the process to be trustworthy; otherwise authentication secrets can easily be compromised. Given the unceasing efforts of attackers worldwide such trustworthiness is increasingly not a given. A variety of technical solutions, such as utilising multiple devices/channels and verification protocols, has the potential to mitigate the threat of untrusted communications to a certain extent. Yet such technical solutions make two assumptions: (1) users have access to multiple devices and (2) attackers will not resort to hacking the human, using social engineering techniques. In this paper, we propose and explore the potential of using human-based computation instead of solely technical solutions to mitigate the threat of untrusted devices and channels. ZeTA (Zero Trust Authentication on untrusted channels) has the potential to allow people to authenticate despite compromised channels or communications and easily observed usage. Our contributions are threefold: (1) We propose the ZeTA protocol with a formal definition and security analysis that utilises semantics and human-based computation to ameliorate the problem of untrusted devices and channels. (2) We outline a security analysis to assess the envisaged performance of the proposed authentication protocol. (3) We report on a usability study that explores the viability of relying on human computation in this context