# Practical of Multi-party FHE (Threshold, Proxy Re-encryption, etc.)?

**URL:** <https://openfhe.discourse.group/t/practical-of-multi-party-fhe-threshold-proxy-re-encryption-etc/1570>\
**Category:** FHE Use Cases\
**Tags:** questions\
**Created:** [September 13, 2024, 8:42am UTC](https://openfhe.discourse.group/t/practical-of-multi-party-fhe-threshold-proxy-re-encryption-etc/1570 "2024-09-13T08:42:11Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![ManhBui](https://avatars.discourse-cdn.com/v4/letter/m/ad7895/32.png) [@ManhBui](https://openfhe.discourse.group/u/ManhBui)\
**Post date:** [September 13, 2024, 8:42am UTC](https://openfhe.discourse.group/t/practical-of-multi-party-fhe-threshold-proxy-re-encryption-etc/1570/1 "2024-09-13T08:42:11Z")

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Hi guys, I hope this question does not bother you since I am generally a newbie in the cryptography system.  
I am exploring the field of Federated Learning and Multi-party FHE (MHE), but the question comes to my mind that in a real-world system, the key pairs must be managed by Key Service Management ( Google Cloud KMS, AWS KMS, etc.) So, do we actually need such advanced techniques (threshold FHE, proxy re-encryption) because, from my understanding, these techniques are applicable in scenarios where users hold their private keys?

I hope you guys can help me with this question.  
Best regards,  
Manh.

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**Author:** ![ypolyakov](https://yyz1.discourse-cdn.com/flex031/user_avatar/openfhe.discourse.group/ypolyakov/32/47_2.png) [@ypolyakov](https://openfhe.discourse.group/u/ypolyakov)\
**Post date:** [September 18, 2024, 12:06am UTC](https://openfhe.discourse.group/t/practical-of-multi-party-fhe-threshold-proxy-re-encryption-etc/1570/2 "2024-09-18T00:06:23Z")

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In the case of threshold FHE, no single user holds a private key. Each user holds a secret share of the private key. I suggest watching the following webinar to get familiar with how threshold FHE works: [Homomorphic Encryption for OpenFHE Users – OpenFHE.org](https://www.openfhe.org/portfolio-item/homomorphic-encryption-for-palisade-users-5/) The webinar also talks about multi-key FHE.

Proxy re-encryption is a different protocol. The user holds its own private key and there is a mechanism to re-encrypt (using a public re-encryption key) an existing ciphertext (encrypted under a different key) using the key of the user who needs to decrypt the ciphertext. This is a delegation capability that is often used in publisher/subscriber systems. See [Fast Proxy Re-Encryption for Publish/Subscribe Systems](https://eprint.iacr.org/2017/410) for more information.