The Universal Composability (UC) framework (FOCS ’01) is the current standard for proving security of cryptographic protocols under composition. It allows to reason about complex protocol structures in a bottom-up fashion: any building block that UC-secure can be composed arbitrarily with other construction while retaining their guarantees. Unfortunately, some properties such as verifiability o...

We present an improvement of Ohkubo et al.’s e-voting protocol [OMA99]: We provide that the validator’s signature is attached directly to the vote although the vote has been encrypted before. Thus verifiability does not end before tallying like in the original scheme but is pervasive even beyond the end of the election. This prevents manipulation of the plaintext votes and offers verifiability ...

As is well-known from the literature on oligopolistic competition with incomplete information, firms have incentives to share private value demand information. However, by assuming verifiability of demand data, these models ignore the possibility of strategic misinformation. We show that if firms can send misleading demand information, they will always do so. Furthermore, we derive a costly sig...

Authentication and confidentiality are the most important security goals to be achieved. This paper proposes a new tripartite signcryption scheme without bilinear pairings. The proposed tripartite signcryption scheme is efficient when three entities want to perform secure transactions as in mobile communication or in e-commerce. The proposed scheme is based on the elliptic curve discrete logari...

This paper describes Scantegrity, an electronic voting system developed by Chaum et al. (2008b), and it analyses Scantegrity’s ability to satisfy the goals of privacy and verifiability. The paper describes a programmatic attack on Scantegrity and presents findings in the form of program output for a corrupted hypothetical election. The attack takes advantage of the inherent vulnerability of ele...

In this paper, we introduce a new functionality for proxy re-encryption (PRE) that we call re-encryption verifiability. In a PRE scheme with re-encryption verifiability (which we simply call verifiable PRE, or VPRE), a receiver of a re-encrypted ciphertext can verify whether the received ciphertext is correctly transformed from an original ciphertext by a proxy, and thus can detect illegal acti...

In electronic voting, we say that a protocol has cast-asintended verifiability if the contents of each encrypted vote can be audited in order to ensure that they match the voter’s selections. It is traditionally thought that this verification can only be performed by the voter who casts the vote, since only she knows the content of her vote. In this work, we show that this is not the case: we p...