Vitalik Buterin, the co-founder of Ethereum, has frequently talked about privacy issues recently, first for the privacy protocol Railgun, and after the U.S. Congress approved a controversial issue in the Foreign Intelligence Surveillance Act last month. After extending the terms for two years and authorizing U.S. intelligence agencies to monitor foreign targets without a search warrant, he criticized the value of cryptocurrency for being under attack.

Vitalik Buterin tweeted on the 5th that many people have recently been interested in fully homomorphic encryption (Fully homomophic Encryption, FHE) technology. Therefore, he republished his article published in 2020, which went into depth. The relevant mathematical working principles of FHE are introduced.

FHE Introduction

Vitalik Buterin pointed out in this article that FHE has long been considered one of the holy grails of cryptography. FHE is an encryption technology that allows third parties to perform calculations on encrypted materials. , and obtain the encrypted result, which the third party can return to anyone who has the decryption key of the original material, but the third party itself cannot decrypt the material or the result itself.

Vitalik Buterin pointed out as an example that a user receives a series of emails and wants to use a third-party spam filter to check whether they are spam.

Generally speaking, spam filters will want to protect the privacy of the algorithm. Either the spam filter provider wants its source code to be closed source, or it will rely on a very large database, and the provider does not want to make this public. Database, because this will make attacks easier, but users who are concerned about the privacy of their data and do not want to upload their unencrypted emails to third parties can use FHE to achieve this.

FHE is widely used

The article mentioned that FHE is widely used, covering the blockchain field, such as light clients that can be used to protect privacy end, the following applications can also be implemented:

• More efficient covert address protocols, and more general scalability solutions for privacy protection protocols. The current privacy protection protocol requires each user Scan the entire blockchain yourself for incoming transactions.

• A privacy-preserving data sharing marketplace that allows users to perform specific calculations on their data while maintaining full control over their data.

• As part of stronger cryptographic primitives, such as more efficient multi-party computation protocols, program obfuscation may eventually also be covered.

What are the differences between FHE, ZK and MPC?

Previously, Portal Ventures wrote an article last year to discuss FHE technology, analyzing its differences with zero-knowledge proof (ZK) and multi-party computation (MPC), pointing out that in the field of cryptocurrency, FHE can be used to build a more private For smart contracts and other blockchain applications, ZK is used to build scalable blockchain solutions, while MPC is mainly used for private key management and custody.

The article mentioned that although FHE, ZK and MPC overlap in some aspects, they all have their own unique advantages and application scenarios. In the currency circle, these three technologies are all for enhancing privacy and The security offers huge potential, but their combination and further research remains an active area in the crypto community.

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