Added private filters concept content (#373)

* Added private filters

Signed-off-by: Madeline Murray <[email protected]>

docs/HowTo/Interact/Filters/Accessing-Logs-Using-JSON-RPC.md

@@ -17,6 +17,10 @@ Use [`eth_newFilter`](../../../Reference/API-Methods.md#eth_newfilter) to create
 using [`eth_getFilterChanges`](../../../Reference/API-Methods.md#eth_getfilterchanges) and
 [`eth_getFilterLogs`](../../../Reference/API-Methods.md#eth_getfilterlogs)).
 
+Access logs for [private contracts](../../../Concepts/Privacy/Privacy-Overview.md) using the equivalent
+[`priv_*` methods and specifying the privacy group ID](#filters-for-private-contracts). For example,
+[`priv_getLogs`](../../../Reference/API-Methods.md#priv_getlogs).
+
 !!! note
 
     The sample contract included in [Events and Logs](../../../Concepts/Events-and-Logs.md) created
@@ -54,7 +58,7 @@ Create a filter using [`eth_newFilter`](../../../Reference/API-Methods.md#eth_ne
 [`eth_newFilter`](../../../Reference/API-Methods.md#eth_newfilter) returns a filter ID hash (for
 example, `0x1ddf0c00989044e9b41cc0ae40272df3`).
 
-### Polling a Filter for changes
+### Polling a filter for changes
 
 To poll the filter for changes since the last poll, use
 [`eth_getFilterChanges`](../../../Reference/API-Methods.md#eth_getfilterchanges) with the filter ID
@@ -150,10 +154,43 @@ When a filter is no longer required, use
 [`eth_uninstallFilter`](../../../Reference/API-Methods.md#eth_uninstallfilter) to remove the
 filter.
 
+## Filters for private contracts
+
+Filters for private contracts are created, accessed, and uninstalled using:
+
+* [`priv_getFilterChanges`](../../../Reference/API-Methods.md#priv_getfilterchanges)
+* [`priv_getFilterLogs`](../../../Reference/API-Methods.md#priv_getfilterlogs)
+* [`priv_getLogs`](../../../Reference/API-Methods.md#priv_getlogs)
+* [`priv_newFilter`](../../../Reference/API-Methods.md#priv_newfilter)
+* [`priv_uninstallFilter`](../../../Reference/API-Methods.md#priv_uninstallfilter).
+
+The [privacy group ID](../../../Concepts/Privacy/Privacy-Overview.md) must be specified as parameter 0
+for the `priv` methods.
+
+!!! example
+
+    ```
+    {
+        "jsonrpc": "2.0",
+        "method": "priv_newFilter",
+        "params": [
+            "4rFldHM792LeP/e2WPkTXZedjwKuTr/KwCFTt6mBbkI=",
+            {
+             "fromBlock": "earliest",
+             "toBlock": "latest",
+             "addresses": ["0x991cc548c154b2953cc48c02f782e1314097dfbb"],
+             "topics": ["0x85bea11d86cefb165374e0f727bacf21dc2f4ea816493981ecf72dcfb212a410"]
+            }
+        ],
+        "id": 1
+    }
+    ```
+
 ## Getting logs using a filter options object
 
 To get all logs for a filter options object, use
-[`eth_getLogs`](../../../Reference/API-Methods.md#eth_getlogs).
+[`eth_getLogs`](../../../Reference/API-Methods.md#eth_getlogs) or [`priv_getLogs`](../../../Reference/API-Methods.md#priv_getlogs)
+for a private contract.
 
 !!! example