This paper will show that Hsu and Wu’s efficient nonrepudiable threshold proxy signature scheme with known signers and Yang, Tzeng and Hwang’s efficient nonrepudiable threshold proxy signature scheme with known signers are insecure. The malicious original signer can forge a valid threshold proxy signature for any message and any warrant after getting a valid proxy signature. In addition, since ...

A (t, n) threshold proxy signature scheme enables an original signer to delegate the signature authority to a proxy group of n member such that t or more than t proxy signers can cooperatively sign messages on behalf of the original signer. In the paper, we review the security of two nonrepudiable threshold proxy signature schemes. We show that Tzeng et al.’s threshold proxy signature scheme is...

Numerous anonymity revocation mechanisms have been proposed for off-line e-cash system in the last decade. Within this category of payment systems, two primary considerations are double-spending detection and tracing capability. However, most designs and existing solutions for these two basic requirements are inefficient or impractical. In this paper, an efficient e-cash with anonymity revocati...

In this letter, we show that Fan-Chen-Yeh’s blind signature scheme and Chien-Jan-Tseng’s partially blind signature scheme are vulnerable to the chosen–plaintext attack. We also show that both schemes can be modified so that the chosen– plaintext attack is impossible. But, still Chien-Jan-Tseng’s partially blind signature scheme is vulnerable. It fails to satisfy the partial blindness property. ...

To strengthen the anonymity of Bitcoin, several centralized coin-mixing providers (mixers) such as BitcoinFog.com, BitLaundry.com, and Blockchain.info assist users to mix Bitcoins through CoinJoin transactions with multiple inputs and multiple outputs to uncover the relationship between them. However, these mixers know the output address of each user, such that they cannot provide true anonymit...

There have been several approaches in the past to obtain signature schemes with appendix and signature schemes giving message recovery based on the discrete logarithm problem. Most of them can be embedded into a Meta-ElGamal and Meta-Message recovery scheme. In this paper we present the Meta-blind signature schemes which have been developed from the ElGamal based blind signature scheme and the ...

An oo-line electronic coin system is presented that ooers multi-party security and unconditional privacy of payments. The system improves signiicantly on the eeciency of the previously most eecient such system known in the literature, due to application of a recently proposed technique called secret-key certiicates. By deenition of secret-key certiicates, pairs consisting of a public key and a ...

Partially blind signature scheme is a cryptographic primitive mainly used to design efficient and anonymous electronic cash systems. Due to this attractive application, some researchers have focused their interest on it. Cao, Lin and Xue recently proposed such a protocol based on RSA. In this paper we first show that this protocol does not meet the anonymous property since the bank is able to l...

In this paper, we propose a robust and verifiable multi-authority secret voting scheme which meets the requirements of large-scale general elections. This scheme uses a uniquely blind threshold signature scheme to get blind threshold electronic votes such that any voter can abstain from voting after the registration phase. It also uses the threshold cryptosystem to guarantee fairness among the ...

Since threshold proxy signature has been proposed, all threshold proxy signature schemes are based on the discrete logarithm problems in the modular multiplicative group which has an element g with a large prime order. Nowadays this kind of threshold proxy signature schemes become more and more complex and time-consuming for security and specific requirement. In this paper, we propose a (biline...