Sybil attacks make blockchains nearly ungovernable as I will show.

Introduction

Sybil attacks are network attacks by entities using several accounts. For example, individuals can create havoc on countless platforms by using many accounts to generate votes, book reviews and forum posts.

Blockchains

Blockchain systems are especially vulnerable to Sybil attacks because they are open, pseudonymous and decentralized. Furthermore, they encourage the use of multiple accounts!

Remedies

Blockchain systems can choose to sacrifice openness, pseudonymity or decentralization. For example, limiting or charging for membership would increase security at the expense of openness. Requiring Social Security numbers would increase security at the expense of pseudonymity. Allowing users with different permissions would increase security at the expense of decentralization.

Likely the best remedies for blockchain systems are reputation systems. These can provide security while preserving openness, pseudonymity and decentralization. For example, Ebay sellers have feedback ratings based on customer satisfaction. Reddit users have karma points based on how much other users like their content. Blockchain reputation systems might rely on various parameters such as account balances and the numbers of transactions sent. Unfortunately, reputation systems cannot yet make blockchain systems completely foolproof. Much more research and development is needed.

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Acknowledgements

I would like to thank IOHK (Input Output Hong Kong) for funding this effort.

License

This work is licensed under the Creative Commons Attribution ShareAlike 4.0 International License.