fix #66 update readme

README.md

@@ -1,30 +1,76 @@
-# Banana Split
+# Banana Split 🍌 · ![Yarn tests](https://github.com/paritytech/banana_split/workflows/Yarn%20tests/badge.svg) [![Join the chat at https://gitter.im/paritytech/banana_split](https://badges.gitter.im/paritytech/banana_split.svg)](https://gitter.im/paritytech/banana_split?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
-![Yarn tests](https://github.com/paritytech/banana_split/workflows/Yarn%20tests/badge.svg)
+Banana Split makes your paper backups more resilient and secure using [Shamir’s secret sharing](https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing).
 
-[![Join the chat at https://gitter.im/paritytech/banana_split](https://badges.gitter.im/paritytech/banana_split.svg)](https://gitter.im/paritytech/banana_split?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+It splits your secret (e.g., paper backup) into `N` pieces, but only requires a majority of those pieces (`N/2+1`) to recover your secret.
 
-## Project setup
+## Why Banana Split?
+There’s a few problems with normal paper backups:
+If you have the whole paper backup somewhere, you’re vulnerable to someone finding it and stealing it—without you ever knowing they did (e.g., they can just take a photo of it).
+If you split your paper backup into two, what happens if one of those pieces goes missing?
+
+For example:
+
+You use Banana Split to split your paper backup into 5 pieces. You then give 5 friends a piece. It only takes 3 of those friends to come together to retrieve the paper backup. If 2 of your friends end up losing their piece, it’s okay. And if 2 of your friends collude and try to retrieve your backup, they won’t be able to.
+That is to say:
+
+**Any 3 friends will know everything; any 2 friends will know nothing.**
+
+## Usage
+### How do you make a Banana Split?
+1. Save the Banana Split [HTML page](https://bs.parity.io/) and **open it in offline mode**.
+2. Type your secret into Banana Split.
+Your secret will be encrypted with an auto-generated passphrase and split it into the number of QR codes you specify.
+3. Print out your QR codes.
+4. **Write the passphrase by hand on every sheet**.
+Doing this by hand protects against an attacker intercepting things you’re sending to the printer.
+
+### How do you retrieve a Banana Split?
+Recovery can be done on any device with a webcam.
+
+1. Save the Banana Split [HTML page](https://bs.parity.io/) and **open it in offline mode**.
+2. Using your webcam, scan in a majority of your QR code printouts (e.g., if you had 7 printouts, you’ll need 4).
+3. Enter your passphrase.
+4. Viola! Your secret is restored.
+
+## ⚠️ Important
+###  Work local and offline
+
+Banana Split is a self-contained HTML page.
+To ensure your precious data is never sent outside, it only works when opened from your local hard drive while your browser is in Offline mode.
+
+### Without the passphrase, you won’t be able to retrieve your secret
+
+To retrieve your secret, you’ll need to have a majority of the printouts and know the passphrase.
+This is why it is critical for you to write the passphrase on every printout.
+
+### Keep the HTML document
+
+This HTML page is a fully self-contained application under GPLv3 license.
+Please feel free to copy and share it with anyone you want to use it. The more copies out there, the less likely it will be compromised or taken down.
+
+## Development
+#### Project setup
 ```
 yarn install
 ```
 
-### Compiles and hot-reloads for development
+#### Compiles and hot-reloads for development
 ```
 yarn run serve
 ```
 
-### Compiles and minifies for production
+#### Compiles and minifies for production
 ```
 yarn run build
 ```
 
-### Run your tests
+#### Run your tests
 ```
 yarn run test:unit
 ```
 
-### Lints and fixes files
+#### Lints and fixes files
 ```
 yarn run lint
 ```