- `/chaincode` is the endpoint used for deploying, invoking, and querying chaincode. Which operation you perform is controlled by the body of the request that you send.

- `/registrar` allows you to enroll users. Why does this matter? Read on!

Calls to the `/chaincode` endpoint of the REST interface require a secure context ID to be included in the body of the request. This means that you must first enroll a user from the user list in the membership service for your network.

If you didn't receive a "Login successful" response, go back and make sure you properly copied your enrollment ID and secret. Now, you have an ID that you can use when deploying, invoking, and querying chaincode in the subsequent steps.

In order to deploy chaincode through the REST interface, you will need to have the chaincode stored in a public git repository. When you send a deploy request to a peer, you send it the url to your chaincode repository, as well as the parameters necessary to initialize the chaincode.

The long string response for the deployment will contain an ID that is associated with this chaincode. The ID is a 128 character alphanumeric hash. Copy this ID on your notepad as well. You should now have a set of enrollID credentials and the cryptographic hash representing your chaincode. This is how you will reference the chaincode in any future Invoke or Query transactions.

Next, let's query the chaincode for the value of `hello_world`, the key we set with the `Init` function.

Hopefully you see that the value of `hello_world` is "hi there", as you specified in the body of the deploy request.

Next, call your generic `write` function by invoking your chaincode and changing the value of "hello_world" to "go away".