Check for existing conjugation key

[crockeea]

With Lattigo v2.1.1, GenRotationKey appears to check if a RotationLeft or RotationRight key exists before generating a new one. This means that calling GenRotationkey(RotationLeft, sk, k, rotKey) twice (with the same k) will only generate one key, which seems like the correct behavior.

However, there is no such check for the Conjugate key: it is generated on every call GenRotationkey(Conjugate, ...), regardless of whether a conjugation key already exists or not. There should probably be a check like there is with RotationLeft/RotationRight so that a conjugation key is only generated once for a particular set of RotationKeys.

[ChristianMct]

Hi @crockeea,

You are absolutely correct. In fact, the evaluation-key generation interface in v2.1.1 has several other issues and we have completely revamped it (as well as the evaluator interface for Relinearization and Rotation/Conjugate) in #100. The idea behind this revamp is that the KeyGenerator interface should be independent of key-management issues such as indexing and storing keys, managing the set of rotation keys etc.

A new version tag including these changes (along with many other improvements) will be released this week.