Function recover_contract_keys 

pub(crate) fn recover_contract_keys(
    sk: SecretKey,
    tpe_agg_pk: &AggregatePublicKey,
    contract: &IncomingContract,
) -> Option<(Keypair, AggregateDecryptionKey)>

The claim keypair and aggregate decryption key of an incoming contract addressed to sk, or none when it is not ours.

Verifying the key is four pairings, so callers run this off the async workers.