Generate automorphism evaluation keys for a set of indices

Generates the eval-key map needed to apply eval_automorphism() at the given set of slot indices. The generated keys are both inserted into the CryptoContext's internal eval-automorphism-key registry (keyed by sk's tag) and returned as an EvalKeyMap handle that the caller can pass directly to eval_automorphism().

Usage

eval_automorphism_key_gen(cc, sk, indices)

Arguments

cc

A CryptoContext.

sk

A PrivateKey.

indices

Integer vector of automorphism indices (not slot indices — use find_automorphism_indices() to compute them from slot indices).

Value

An EvalKeyMap with one entry per input index.

Details

On the C++ side this is equivalent to calling EvalAutomorphismKeyGen(sk, indices) which internally calls CryptoContextImpl::InsertEvalAutomorphismKey with the generated map (cryptocontext.h line 2237). The dual return / registry-insert pattern matches the openfhe-python behavior at the equivalent entry point.

Companion to eval_rotate_key_gen() (reached via key_gen()'s rotations argument): both populate the same cc-internal storage. The automorphism form gives raw access to the automorphism group element (bypassing the rotate-to-automorphism slot mapping that eval_rotate_key_gen performs internally).

See also

eval_automorphism(), find_automorphism_indices()