A verifiably encrypted signature can convince the verifier that a given cipher-text is the encryption of a signature on a given message. It is often used as a building block to construct optimistic fair exchange. Recently, Gu et.al gave an ID-based verifiably encrypted signature scheme and claimed that their scheme was secure in random oracle model. Unfortunately, in this works, we show that th...

Optimistic fair exchange (OFE) is a protocol for solving the problem of exchanging items or services in a fair manner between two parties, a signer and a verifier, with the help of an arbitrator which is called in only when a dispute happens between the two parties. In almost all the previous work on OFE, after obtaining a partial signature from the signer, the verifier can present it to others...

Non-interactive designated verifier (NIDV) proofs were first introduced by Jakobsson et al. and have widely been used as confirmation and denial proofs for undeniable signature schemes. There appears to be no formal security modelling for NIDV undeniable signatures or for NIDV proofs in general. Indeed, recent work by Wang has shown the original NIDV undeniable signature scheme of Jakobsson et ...

Attribute based group signature (ABGS) is a a new generation of group signature schemes. In such a scheme the verifier could define the role of a signer within the group. He determines the attributes possessed by the member signing the document. In this paper we propose the first ABGS scheme with multi-authorities and define its security notions. We construct an ABGS that is proved to be fully ...

This paper shows some insecurities in Xu’s forward secure multi-proxy signature scheme. There are two kinds of attacks on this scheme: (1) anyone can forge some certain messages which to be sign and cannot detect by the signature verifier. (2) This scheme can’t resist the dishonest signer forgery attack by forging its own public key. After that, the paper proposed two new forward-secure multi-p...

Although many watermarking schemes consider the case of universal verifiability, it is undesirable in some applications. Designated verification is a possible solution for this problem. Watermarking scheme with (non-interactive) designated verification through non-invertible schemes was proposed by Lee et al [11] in 2003, to resolve multiple watermarking problem. Yoo et al [14] proposed a very ...

Undeniable signatures, introduced by Chaum and van Antwerpen, and designated confirmer signatures, introduced by Chaum, allow a signer to control the verifiability of his signatures by requiring a verifier to interact with the signer to verify a signature. An important security requirement for these types of signature schemes is non-transferability which informally guarantees that even though a...

Voting schemes that provide receipt-freeness prevent voters from proving their cast vote, and hence thwart vote-buying and coercion. We analyze the security of the multi-authority voting protocol of Benaloh and Tuinstra and demonstrate that this protocol is not receiptfree, opposed to what was claimed in the paper and was believed before. Furthermore, we propose the first practicable receipt-fr...