Backend-Delivered SIP Configuration Keeps Secrets Out of Factory Images

Per-device PBX credentials should be provisioned after identity is established, not cloned into every unit.

The useful question in Backend-Delivered SIP Configuration Keeps Secrets Out of Factory Images was where the behaviour actually originated. LOUP firmware receives server, port, transport, realm, username and password from the backend for its own SIP identity.

This lets manufacturing flash one firmware artifact while the backend assigns unique telephony credentials later. A stolen factory image therefore does not automatically reveal a fleet-wide PBX account, and one device can be revoked without changing every unit.

I treated the known-good configuration as a control sample, changed only the layer under investigation, and recorded the regression or improvement before the next experiment. Evidence marker: backend-sip-provisioning.

Factory reproducibility and runtime identity should be separate. One binary can serve many devices without sharing one secret. Keeping the rule explicit means the same decision can be checked again on the next board revision or firmware branch.

Project evidence

LOUP engineering marker: backend-sip-provisioning. This note records the design or debugging lesson without publishing device credentials, private keys, customer data or manufacturing secrets.