Add NIP-XX: Static Payment Addresses

XX.md

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+# NIP-XX
+
+## Static Payment Addresses
+
+`draft` `optional`
+
+## Abstract
+
+This NIP defines a standardized method for publishing static payment addresses using a dedicated event kind, allowing users to advertise their preferred payment methods across multiple cryptocurrencies and networks.
+
+## Motivation
+
+Users want to publish their payment addresses in a standardized way that is interoperable across Nostr clients. This creates a dedicated event type that clients can fetch only when needed, such as when viewing a user's profile or donation page.
+
+## Specification
+
+### Event Kind
+
+This NIP introduces **kind 10780** for static payment addresses.
+
+### Event Structure
+
+```json
+{
+  "kind": 10780,
+  "content": "",
+  "tags": [
+    ["BTC", "bitcoin", "bc1qxy2kgdygjrsqtzq2n0yrf2493p83kkfjhx0wlh"],
+    ["BTC", "lightning", "[email protected]"],
+    ["ETH", "ethereum", "0x742d35Cc6634C0532925a3b2F0E5f4C96C60BcEe"],
+    ["XMR", "monero", "4A5BNZmM5VXyU2P7J8Q3hY8wXD2E8L9G3qZ2vF1H7sR4cN8xY6fL2mK9qW3eT5r"],
+    ["LBTC", "liquid", "lq1qqf7ns3aawy8k3gv6v6zhqjcw99e8v0fyxrc0ewz3vkclfslp7y9c24k8xm6l3j"]
+  ],
+  // other fields...
+}
+```
+
+### Tag Structure
+
+Each tag MUST have exactly 3 elements:
+1. `<asset>`: The asset ticker (case-sensitive, uppercase recommended)
+2. `<network>`: The network identifier (case-sensitive, lowercase recommended)  
+3. `<address>`: The receiving address for the specified asset on the specified network
+
+### Supported Assets and Networks
+
+Clients SHOULD support the following common combinations:
+
+#### Bitcoin (BTC)
+- `bitcoin`: Bitcoin mainnet (addresses: bc1..., 1..., 3...)
+- `lightning`: Lightning Network (lightning addresses: [email protected] only)
+
+#### Liquid Bitcoin (LBTC)
+- `liquid`: Liquid Network sidechain (addresses: lq1...)
+
+#### Ethereum (ETH)  
+- `ethereum`: Ethereum mainnet (addresses: 0x...)
+
+#### Monero (XMR)
+- `monero`: Monero mainnet (standard Monero addresses)
+
+#### Tether USD (USDT)
+- `ethereum`: USDT on Ethereum
+- `liquid`: USDT on Liquid Network  
+- `tron`: USDT on Tron (addresses: TRX...)
+
+Clients MAY support additional assets and networks beyond this list.
+
+## Implementation Guidelines
+
+### Client Behavior
+
+1. **Fetching**: Clients SHOULD fetch payment address events only when needed (e.g., when viewing a profile or donation interface)
+
+2. **Display**: Clients SHOULD display both the asset name and network for clarity (e.g., "BTC (Lightning)", "USDT (Ethereum)")
+
+3. **User Interface**: Clients SHOULD provide mechanisms for users to easily copy addresses or display QR codes
+
+4. **Ordering**: Multiple `payment` tags MAY be interpreted as the user's preferred payment methods in order of appearance
+
+5. **Validation**: Clients MAY implement basic format validation for addresses on supported networks
+
+6. **Unknown Assets/Networks**: Clients SHOULD gracefully handle unknown asset or network identifiers by displaying them as-is
+
+## Address Format Examples
+
+- **Bitcoin mainnet**: `bc1qxy2kgdygjrsqtzq2n0yrf2493p83kkfjhx0wlh`
+- **Bitcoin Lightning**: `[email protected]` (lightning addresses only)
+- **Liquid Network**: `lq1qqf7ns3aawy8k3gv6v6zhqjcw99e8v0fyxrc0ewz3vkclfslp7y9c24k8xm6l3j`
+- **Ethereum**: `0x742d35Cc6634C0532925a3b2F0E5f4C96C60BcEe`
+- **Tron**: `TRX9QqJo6UbgJ1CXr5wQv9vJ2N8KdGhH9L`
+- **Monero**: `4A5BNZmM5VXyU2P7J8Q3hY8wXD2E8L9G3qZ2vF1H7sR4cN8xY6fL2mK9qW3eT5r`
+
+## Security Considerations
+
+- Users SHOULD verify their addresses are correct before publishing
+- Clients SHOULD warn users when addresses don't match expected formats
+- Lightning addresses SHOULD be tested to verify that invoices can be fetched from them
+- Users SHOULD be aware that payment addresses are public and permanently associated with their Nostr identity
+- Consider the privacy implications of publishing payment addresses
+
+## Future Extensions
+
+This specification may be extended in the future to include:
+- Additional standardized assets and networks
+- Optional metadata fields for payment preferences
+- Integration with other payment protocols
+- Support for dynamic payment requests