A aggregation function for an encrypted vector (add_many/multiply_many)

[Christopher-Wang]

Feature Description

A single encrypted TenSEAL vector should be able to be naively aggregated by either a sum or product.

Is your feature request related to a problem?

This would be especially useful for common operations such as dot product and euclidean distance.

What alternatives have you considered?

Currently the only known method I understand might for summation work is to perform a matrix multiplication with an identity vector which is not ideal.

Additional Context

Ideally the operation would look something like
encrypted_vec.add_many()

[youben11]

Hi @Christopher-Wang and thanks for your input!

I just want to clarify your feature request, so by encrypted_vec.add_many() do you mean summing up the slots of the vector? like if you have a vector encrypting the vector [1, 2, 3], this method will result in a vector encrypting a single value ([6]), is that right?

[Christopher-Wang]

Yes. Similar to the Evaluator::multiply_many and Evaluator::add_many definitions in the SEAL 2.0 documentation. I also check and currently there is no way to encrypt a matrix therefore the matmul workaround is impossible. What steps do you think need to be followed to include that functionality?

[youben11]

Evaluator::multiply_many and Evaluator::add_many actually do the operations on many ciphertexts in an element-wise fashion, and not on the slots of the same ciphertext.

If what you meant is the feature I described in my last comment, it shouldn't be a big deal to implement, it just wasn't a priority, but since there is a need for that, I can take a look at it and ping you when a PR is ready, you can also help us with reviews to let us know if the API for doing those operations looks good. Does this work for you?

[Christopher-Wang]

I do mean the feature in your last comment. Perfect thanks! I appreciate it.