# Signature PlugIn Help

Signature PlugIn adds a signature to any response made through it. It does this by adding a _signature channel to any response.
Signature PlugIn also automatically checks and verifies signed responses. It does this by verifying any _signature channel it detects.
You can setup a signature at both source and sink, and the sink can be assured that any response it receives has a matching signature. Responses that don't match a signature are rejected and a null response is returned.
The signature is a message digest incorporating the source data, the timestamp, and the signature-password provided upon startup. The signature password itself is never transmitted, it is a symmetric secret key.
A simple usage example is to use the same Signature plugin to both generate and check a signature, as in: Signature/Signature/Source/chan.