added salt

Author: shannona

_data/navigation.yml

@@ -212,6 +212,8 @@ envelope:
       url: /envelope/permits/  
     - title: "Request & Response"
       url: /envelope/request/
+    - title: "Salt"
+      url: /envelope/salt/
 envelopecli:
   - title: "Envelope CLI"
     children:

_pages/tech/data-format/envelope-salt.md

@@ -0,0 +1,46 @@
+---
+cover: false
+header:
+  overlay_color: "#000"
+  overlay_filter: "0.25"
+  overlay_image: /assets/images/dev-data-background.jpg
+  og_image: /assets/images/bc-card.jpg
+title: Salting
+hide_description: true
+classes:
+  - wide
+permalink: /envelope/salt/
+sidebar:
+  nav: envelope
+redirect_from:
+  - /salt/
+  - /salting/
+  - /envelope/salting/
+---
+
+## Overview
+
+Salting is a critical privacy enhancement for that keeps elided data
+private. It ensures that even when the same information is elided from
+multiple documents, the resulting hashes are different, preventing
+correlation attacks.
+
+## Why is Salting Important?
+
+Without salting, elision would have a serious privacy weakness:
+
+- Identical content would produce identical hashes.
+- An observer could determine if the same information was elided in multiple documents.
+- Common values could be guessed through dictionary attacks.
+
+### How Does Salting Work?
+
+Salting solves this problem by adding random data to an Envelope leaf
+or node before hashing:
+
+```
+Without salt:  hash("name": "John Smith") → always the same hash
+With salt:     hash("name": "John Smith" + random_salt) → different hash each time
+```
+
+Salts should be cryptographically random and of sufficient length.

_pages/tech/data-format/envelope.md

@@ -206,6 +206,7 @@ _See the [Gordian Envelope playlist](https://www.youtube.com/playlist?list=PLCkr
 * [**Known Values**](/known-values/)
 * [**Permits**](/envelope/permits/)
 * [**Request/Response**](/envelope/request/)
+* [**Salt**](/envelope/salt/)
 
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