Comparison sequence of enc_numbers

[jahidhasanlinix]

I have some questions, say I have a set or sequence of encrypted numbers outsourced to the cloud. Now client sent an encrypted range query to the server. Now I want the server to do the computation and return the value whose range is greater or equal to (>=) given numbers (ignore the lower numbers, filtered). How can this be implemented using concrete, any library, or pseudocode that explains this setup? Any help

[umut-sahin]

Is this what you're looking for?

import numpy as np
from concrete import fhe

configuration = fhe.Configuration(
    enable_unsafe_features=True,
    use_insecure_key_cache=True,
    insecure_key_cache_location=".keys",
    single_precision=False,
)

@fhe.compiler({"numbers": "encrypted", "query": "encrypted"})
def filtering(numbers, query):
    is_greater = numbers > query

    shifted_numbers = numbers * 2  # open space for a single bit at the end
    combined_numbers_and_is_greater = shifted_numbers + is_greater  # put is_greater to that bit

    def extract(combination):
        is_greater = (combination % 2) == 1  # extract is_greater back from packing
        if_true = combination // 2  # if is greater is true, we unpack the number and use it
        if_false = 0  # otherwise we set the element to zero
        return np.where(is_greater, if_true, if_false)  # and apply the operation

    return fhe.univariate(extract)(combined_numbers_and_is_greater)

inputset = [
    (
        np.random.randint(0, 10, size=(5,)),
        np.random.randint(0, 10, size=()),
    )
    for _ in range(100)
]
circuit = filtering.compile(inputset, configuration, verbose=True)

print(filtering(np.array([1, 3, 2, 5, 4]), 3))
print(circuit.encrypt_run_decrypt([1, 3, 2, 5, 4], 3))

prints

[0 0 0 5 4]
[0 0 0 5 4]

Few notes:

• It's impossible to return just to numbers because the server cannot know how many of the values are greater. Thus, we set the rest to 0.
• It's not possible to have a dynamic number of inputs, in this case the size was set to 5 from the inputset and it cannot be called with 6 elements. This is due to how the compiler works. I can explain more if you want.

Let us know if this helps!

[aquint-zama]

FYI this workaround is part of the new tutorial page in the documentation
Closing this issue.