The Secret Manager Local Service component is a core dependency of the connectors created by Integration Builder. It contains methods to cipher and decipher information.
The recommended way to have this component is to install or update it through Integration Builder since that will ensure its version is compatible with the connectors.
Since this is a Supported component you won't be able to see or change its code.
Adding reference to Google.Protobuf.dll due to breaking changes introduced by Platform Server on version 11.18.0