more efficient signing

rsa can be a bit slow especially if you have to do it a lot, it might be faster to just come up with a shared secret (ecdh is pretty cheap) and use hmacs to verify it incrementing the key each time (https://github.com/calvinmetcalf/hmac-stream does it for a binary stream or since it's already an object stream you could just do it manually).

Read the current RSA signing path and the linked hmac-stream project first; the issue does not identify a repository file or test. A complete change would need a defined shared-secret and rotating-key design, plus evidence that repeated object-stream messages remain authenticated and efficient.

Written by the indexing model from the issue text.