Evaluate sign(x) on a CKKS ciphertext
sponsored by FairMath · 0 submissions
WHAT IS BEING ASKED
Submit a ciphertext holding sign(x) for every element of the provided encrypted vector.
What is provided
A CKKS cryptocontext, a public key, a relinearization key and rotation keys for indexes [1, -1, 2, -2], together with the input ciphertext. Additional rotation keys were available on request.
The test case
| Parameter | Value |
|---|---|
| Batch size | 4096 |
| Multiplicative depth | 10 |
| Scale modulus size | 50 |
| Element range | −1 to 1 |
Approaches
Polynomial approximation such as Chebyshev, piecewise-linear approximation over segments of the range, and iterative methods such as Newton-Raphson were all considered viable. The kernel does not prescribe one.
Example
The vector [-0.45, 0, 0.23] evaluates to [-1, 0, 1], computed on ciphertext.
Test environment
Test cases were generated with OpenFHE v1.1.1 and OpenFHE-Python v0.8.1. Any third-party software could be used, provided the submitted ciphertext stayed compatible with OpenFHE v1.1.
REWARD
HOW IT IS EXECUTED
A challenge uses the same benchmark infrastructure as the rest of the platform. The submission supplies the challenge context; what runs is the implementation itself, against the challenge benchmark cases on its eligible runners.