Manage Keys

Concrete generates keys for you implicitly when they are needed and if they have not already been generated. This is useful for development, but it's not flexible (or secure!) for production. Explicit key management API is introduced to be used in such cases to easily generate and re-use keys.

Definition

Let's start by defining a circuit:

from concrete import fhe

@fhe.compiler({"x": "encrypted"})
def f(x):
    return x ** 2

inputset = range(10)
circuit = f.compile(inputset)

Circuits have a property called keys of type fhe.Keys, which has several utility functions dedicated to key management!

Generation

To explicitly generate keys for a circuit, you can use:

circuit.keys.generate()

And it's possible to set a custom seed for reproducibility:

circuit.keys.generate(seed=420)

Serialization

To serialize keys, say to send it across the network:

serialized_keys: bytes = circuit.keys.serialize()

Deserialization

To deserialize the keys back, after receiving serialized keys:

keys: fhe.Keys = fhe.Keys.deserialize(serialized_keys)

Assignment

Once you have a valid fhe.Keys object, you can directly assign it to the circuit:

circuit.keys = keys

Saving

You can also use the filesystem to store the keys directly, without needing to deal with serialization and file management yourself:

circuit.keys.save("/path/to/keys")

Loading

After keys are saved to disk, you can load them back via:

circuit.keys.load("/path/to/keys")

Automatic Management

If you want to generate keys in the first run and reuse the keys in consecutive runs:

circuit.keys.load_if_exists_generate_and_save_otherwise("/path/to/keys")