A Blind-Mixing Scheme for Bitcoin based on an Elliptic Curve Cryptography Blind Digital Signature Algorithm

TL;DR

This paper introduces a new centralized Bitcoin coin-mixing scheme using elliptic curve blind signatures to enhance user anonymity and prevent linkability between input and output addresses.

Contribution

It proposes a novel elliptic curve based blind signature scheme for Bitcoin mixing, improving speed and security over existing methods.

Findings

Blind-Mixing is 10.5 times faster than RSA Coin-Mixing.

BlindCoin can be deanonymized due to its public log.

Blind-Mixing effectively prevents linkability between addresses.

Abstract

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 anonymity. This paper proposes a centralized coin-mixing algorithm based on an elliptic curve blind signature scheme (denoted as Blind-Mixing) that obstructs mixers from linking an input address with an output address. Comparisons among three blind signature based algorithms, Blind-Mixing, BlindCoin, and RSA Coin-Mixing, are conducted. It is determined that BlindCoin may be deanonymized because of its use of a public log. In RSA Coin-Mixing, a user's Bitcoins may be falsely claimed by another. In addition, the blind signature scheme of Blind-Mixing executes 10.5 times faster than that of RSA Coin-Mixing.