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Huelse / SEAL-Python

Microsoft SEAL 4.X For Python
MIT License
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Is there a function for sum of an encrypted vector? #55

Closed lidh15 closed 3 years ago

lidh15 commented 3 years ago

I checked the methods of Evaluator class and failed to find a sum or mean value calculator. Currently, I'm doing it like rotate vector by one slot and add it to the sum. But this is too slow to apply out of a demo. Is there a solution or seal is not going to support such operations?

Huelse commented 3 years ago

Sorry for reply late, I didn't receive the email from Github or missed it, if you are using the ckks scheme, you can get the sum of a vector like this:

slot_count = ckks_encoder.slot_count()
for i in range(int(math.log(slot_count, 2))):
    temp = evaluator.rotate_vector(ct, 1 << i, gk)
    evaluator.add_inplace(ct, temp)

And you can multiply float(1/slot_count) with a sum ciphertext, it will be close to the mean value if the scale is valid.