Is it feasible to generate a RotateKeyGen without specifying EvalBootstrapSetup({4, 4}, {0, 0}, 16384)?

[yellow123Nike]

Is it feasible to generate a RotateKeyGen without specifying EvalBootstrapSetup({4, 4}, {0, 0}, 16384)?

[narger-ef]

Yes, you can generate rotation keys without bootstrapping. Notice that, in this case, you will not be able to perform bootstrap anymore.

[yellow123Nike]

However, the following error occurred at res = m_cc->EvalAdd(res, m_cc->EvalRotate(sum, 1024));.

[narger-ef]

This happens because $1024 \neq -1024$. I think that the actual rotation for $-1024$ is $16384-1024=15360$

[yellow123Nike]

However, after adding context->EvalBootstrapSetup({4, 4}, {0, 0}, 16384);, this issue did not occur. Apologies, I am a beginner in FHE.

[narger-ef]

No worries, I am still learning, too :-P.

The bootstrapping its self uses a lot of rotation keys, perhaps that setup generates the key also for $15360$.

To confirm, check the memory when you

• generate the bootstrapping keys vs
• generate the bootstrapping keys + rotation keys 15360.

If they are the same, then the rotation key for $15360$ is already included in the ones used by the bootstrapping

[yellow123Nike]

Thank you very much!

[narger-ef]

Feel free to re-open if you have issues :)

[yellow123Nike]

Why is the error from layer 3 to FC so large?