botfights/.claude/skills/nostr-auth/nostr-auth.md

---
description: Nostr keypair authentication for the Syntropy Institute portal (auth only, no relays)
match:
  - nostr
  - auth
  - login
  - keypair
  - sign
  - challenge
---

# Nostr Auth Skill

## When to Use
When working with authentication flows, keypair management, or NIP-98 API auth in the portal.

## Key Principle
Nostr is used ONLY for cryptographic authentication. No relay connections. No event publishing. Just keypairs and signatures.

## Keypair Generation (Easy Mode)
```typescript
import { generateSecretKey, getPublicKey, nip19 } from 'nostr-tools';

// Generate new identity
const secretKey = generateSecretKey(); // Uint8Array
const publicKey = getPublicKey(secretKey); // hex string

// Encode for display (only when user requests it)
const npub = nip19.npubEncode(publicKey);
const nsec = nip19.nsecEncode(secretKey);
```

## Private Key Encryption (for localStorage)
```typescript
// Encrypt private key with user's passphrase before storing
async function encryptPrivateKey(secretKey: Uint8Array, passphrase: string): Promise<string> {
  const encoder = new TextEncoder();
  const keyMaterial = await crypto.subtle.importKey(
    'raw', encoder.encode(passphrase), 'PBKDF2', false, ['deriveKey']
  );
  const salt = crypto.getRandomValues(new Uint8Array(16));
  const derivedKey = await crypto.subtle.deriveKey(
    { name: 'PBKDF2', salt, iterations: 600000, hash: 'SHA-256' },
    keyMaterial, { name: 'AES-GCM', length: 256 }, false, ['encrypt']
  );
  const iv = crypto.getRandomValues(new Uint8Array(12));
  const encrypted = await crypto.subtle.encrypt(
    { name: 'AES-GCM', iv }, derivedKey, secretKey
  );
  // Return salt + iv + ciphertext as base64
  const combined = new Uint8Array([...salt, ...iv, ...new Uint8Array(encrypted)]);
  return btoa(String.fromCharCode(...combined));
}
```

## NIP-07 Detection (Nostr Native)
```typescript
// Check for browser extension
function hasNostrExtension(): boolean {
  return typeof window !== 'undefined' && 'nostr' in window;
}

// Sign with extension
async function signWithExtension(event: object): Promise<object> {
  return await (window as any).nostr.signEvent(event);
}

// Get public key from extension
async function getExtensionPubkey(): Promise<string> {
  return await (window as any).nostr.getPublicKey();
}
```

## Challenge-Response Auth (NIP-98 style)
```typescript
import { finalizeEvent, verifyEvent } from 'nostr-tools';

// Client: Sign auth challenge
function createAuthEvent(secretKey: Uint8Array, url: string, method: string) {
  const event = finalizeEvent({
    kind: 27235, // NIP-98 HTTP Auth
    created_at: Math.floor(Date.now() / 1000),
    tags: [
      ['u', url],
      ['method', method],
    ],
    content: '',
  }, secretKey);
  return event;
}

// Send as Authorization header:
// Authorization: Nostr <base64-encoded-event-json>

// Server: Verify auth event
function verifyAuthEvent(event: any, expectedUrl: string, expectedMethod: string): boolean {
  if (!verifyEvent(event)) return false;
  if (event.kind !== 27235) return false;
  const urlTag = event.tags.find((t: string[]) => t[0] === 'u');
  const methodTag = event.tags.find((t: string[]) => t[0] === 'method');
  if (urlTag?.[1] !== expectedUrl) return false;
  if (methodTag?.[1] !== expectedMethod) return false;
  // Check timestamp is within 60 seconds
  if (Math.abs(Date.now() / 1000 - event.created_at) > 60) return false;
  return true;
}
```

## Rules
- NEVER store private keys on the server
- NEVER connect to any Nostr relay
- NEVER transmit private keys over the network
- ALWAYS encrypt private keys before storing in localStorage
- Use PBKDF2 with at least 600,000 iterations for key derivation
- Auth events expire after 60 seconds
- Server only stores npub (public key)