Fhe algorithms used by zama

Zama fhEVM
1

Hello,

I was reading about some fhe algorithms like Brakerski-Fan-Vercauteren (BFV), Brakerski-Gentry-Vaikuntanathan (BGV) and Cheon-Kim-Kim-Song (CKKS).

Could you please confirm which algorithm is used by zama for fully homomorphic encryption and calculations?

Thanks

2

Hello,

sorry for the late answer. Zama uses TFHE, also called CGGI (Chillotti, Gama, Georgieva, Izabachène), Faster Fully Homomorphic Encryption: Bootstrapping in less than 0.1 Seconds and further improvements. More info in this blog, TFHE Deep Dive - Part I - Ciphertext types , eg

Cheers

3

Thank you for the response.

I have a couple of more questions.

Is there a specific number of nodes that need to get together to perform the decryption of encrypted data (like one third or half of the nodes)?

Also, how is re-encryption done securely since the data is being decrypted and then encrypted again. is the decryption done on the evm or in memory ?

4

The decryption and reencryption processes are conducted on a separate network; neither the blockchain nor the EVM possesses the private key or any part of it.
For this network, we employ threshold cryptography. The multi-party paradigm of threshold cryptography facilitates threshold schemes for securely distributing trust in decryption operations. Each party holds a portion of the private key and cannot decrypt independently; however, as it currently stands, participation from at least one-third is necessary.
The reencryption process differs slightly. A user requesting reencryption will receive multiple reencrypted parts to reassemble, ensuring that the complete value is never fully decrypted at any point.