Overview

The adoption of Fully Homomorphic Encryption (FHE) algorithms can be classified into different categories due to the variety of FHE algorithms and their usage patterns.

FHE Variants

There are different types of FHE algorithms based on key usage, including:

• Single-Key FHE: In this variant, all homomorphic operations are performed using a single encryption key. The same key is used to encrypt the data, perform computations on the encrypted data, and decrypt the result. This simplifies key management since only one key is involved in the entire process.

• Threshold FHE: This combines FHE with threshold cryptography to enable distributed, secure computations on encrypted data. In a threshold FHE scheme, a group of nodes collaboratively generate a shared public key, with each node holding a part of the decryption key. Homomorphic computations are performed on data encrypted with the shared public key, and the result is decrypted by a subset of nodes in the group.

Use Case Variants

In BAVO's zkFHE network, various applications (callers) can initiate FHE computations from BAVO workers. There are three primary application modes to accommodate different types of callers. Further workflow details of these modes are available in the technical section.

• Single-User Mode: A single user provides one or multiple pieces of data for a computation task, all encrypted with the user's public key. This is a standard FHE-based outsourced computation, where the user delegates encrypted tasks and utilizes the zkFHE network's computational power.

• Joint-Worker Mode: Multiple users can provide data for a computation task, with all data encrypted using a shared public key generated by a group of BAVO workers. This is a typical application of Threshold FHE within BAVO's network.

• Selective Multi-Worker Mode: In this mode, data from one or multiple users is encrypted using the public keys of different workers. A group of workers is selected by the caller in advance to perform the computation. It’s generally not recommended to encrypt user data with a worker’s public key due to potential privacy risks, though this mode allows for such flexibility.

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