Overview of Fully Homomorphic Encryption Technology and Analysis of Application Scenarios

Fully Homomorphic Encryption ( FHE ) is an advanced encryption technology that allows computation on encrypted data directly without the need for decryption. Unlike traditional static encryption and transmission encryption, FHE supports complex data processing while protecting privacy.

The core advantage of FHE is that it can execute arbitrary function operations in the ciphertext state, with the output still in encrypted form. This allows sensitive data to be securely processed in untrusted environments, such as cloud computing platforms. The security of FHE is based on cryptographic algorithms and does not rely on hardware, thus effectively preventing various types of side-channel attacks.

FHE systems typically include three types of keys:

1. Decryption Key: Master Key, used to decrypt the final result.
2. Encryption Key: Used for encrypting the original data.
3. Calculate Key: Used for performing homomorphic operations on ciphertext.

FHE has various application modes:

• Outsourcing model: Hand over encrypted data to a third party for processing, suitable for scenarios such as PIR.
• Two-party computing model: Both parties provide their private data for joint computation.
• Aggregation Mode: Summarizes data from multiple parties, applied in federated learning, electronic voting, etc.
• Client-Server Model: The server provides the AI model, and the client provides private data.

Although FHE has a high computational cost, it has unique advantages in scenarios with high privacy protection requirements. In the future, with the development of dedicated hardware, FHE is expected to be more widely used.

In practical applications, FHE can verify the correctness of calculations by introducing redundant computations, digital signatures, and other methods. At the same time, mechanisms such as key sharing can be used to control decryption permissions. The development of FHE will bring new possibilities to the field of privacy computing.