Cashu

Introduction to Cashew

• Cashew is a protocol designed for facilitating Bitcoin banking operations. It leverages the concept of blinded servers to enhance privacy, allowing for the secure issuance and management of electronic cash (ecash) notes.
• Cashu workshop YouTube

• twitter link to the render loading below https://twitter.com/callebtc/status/1777598819355496587

References and Resources

• Direct users to important resources for deeper exploration and troubleshooting:
• Cashew Documentation:
• Cashew GitHub Repository
• Get started with eNuts
• Cashu Token Decoder (nostrapps.github.io)

Workshop stuff

Prerequisites

• Before beginning, ensure you have:
  • A modern web browser for testing your wallet.
  • A text editor or IDE (e.g., Visual Studio Code, Sublime Text) for writing and editing code.
  • Access to the internet to fetch resources and documentation from the Cashew GitHub repository.

Setup Environment

Create Project Directory

• Make a new folder on your computer named cashew_wallet.

Initialize Project File

• Inside this folder, create a file named index.html.
• Open index.html in your preferred code editor.
• Set up a basic HTML skeleton with the <html>, <head>, and <body> tags.

Implementing Cashew Functionality

Wallet Interface Setup

• Add basic HTML to create buttons for sending and receiving ecash.
• Example:

  <button id="sendBtn">Send eCash</button>
  <button id="receiveBtn">Receive eCash</button>

Fetching Keysets from Cashew Mint

• Use JavaScript to asynchronously fetch the list of available keysets from the Cashew mint’s API.
• This step is crucial for understanding which denominations of ecash your wallet can handle.
• Example API call: fetch('https://cashew-mint.example/api/keysets').then(response => response.json())

Generating a Secret for Blind Signatures

• Implement JavaScript code to generate a new secret key. This key will be essential for creating blind signatures, a cornerstone of Cashew’s privacy features.
• Utilize cryptographic libraries available in JavaScript for secure key generation.

Creating and Paying a Lightning Invoice

• Generate a lightning invoice for depositing Bitcoin into your Cashew wallet. This involves interacting with the Cashew mint to issue the invoice.
• Implement a function to check the payment status of the invoice, waiting for confirmation before proceeding.

Requesting a Blinded Signature from the Mint

• Once the invoice payment is confirmed, request a blinded signature for a specified ecash amount from the mint. This signature is necessary for the mint to acknowledge your ecash holdings without compromising privacy.

Unblinding the Signature

• Use the previously generated secret key to unblind the mint’s signature. This process converts the blinded signature into a form usable for transactions while maintaining the integrity of the privacy guarantees.

Sending and Receiving Ecash

Sending Ecash

• Create functionality to allow users to send ecash by generating a transaction (nut) with the unblinded signature and a specified amount.
• Include input fields for the recipient’s address and the amount to be sent.

Receiving Ecash

• Implement the ability to receive ecash by processing transactions from others. Validate these transactions with the Cashew mint to ensure they have not been double-spent.

Advanced Features (Optional)

• Expand upon the basic wallet functionality by exploring advanced features such as:
  • Supporting transactions of multiple ecash denominations.
  • Implementing a withdrawal feature to convert ecash back into Bitcoin.
  • Adding multisig capabilities for enhanced security.