// Secure key generation requirements
interface KeyGeneration {
  // Minimum entropy: 256 bits
  entropy: Uint8Array;  // Must be cryptographically random
  
  // Key type determines algorithm
  algorithm: 'ed25519' | 'secp256k1' | 'x25519';
  
  // Derivation path for hierarchical keys
  derivationPath?: string;
}

interface EncryptedKey {
  // Argon2id parameters
  argon2: {
    memory: 256 * 1024;  // 256MB
    iterations: 3;
    parallelism: 4;
    saltLen: 32;
  };
  
  // Encryption
  algorithm: 'XChaCha20-Poly1305';
  nonce: Uint8Array;  // 24 bytes
  ciphertext: Uint8Array;
  tag: Uint8Array;    // 16 bytes
}

interface ContentSignature {
  // Algorithm identifier
  algorithm: 'ed25519';
  
  // Public key of signer
  publicKey: Uint8Array;
  
  // Signature bytes (64 for Ed25519)
  signature: Uint8Array;
  
  // Timestamp (prevents old content replay)
  signedAt: number;
}

function verifyContent(content: ContentObject): VerificationResult {
  const checks = [
    // 1. Signature validity
    verifySignature(content),
    
    // 2. Hash integrity
    verifyHash(content),
    
    // 3. Timestamp reasonability
    verifyTimestamp(content, tolerance: 5 * 60 * 1000),
    
    // 4. Author key validity
    verifyAuthorKey(content.author),
    
    // 5. Zone membership (if applicable)
    verifyZoneMembership(content.zone, content.author),
  ];
  
  return {
    valid: checks.every(c => c.passed),
    checks,
  };
}

interface MultiRecipientPayload {
  // Encrypted content key
  encryptedKeys: {
    recipient: DID;
    encryptedKey: Uint8Array;  // Key encrypted to recipient
  }[];
  
  // Content encrypted with symmetric key
  encryptedContent: {
    nonce: Uint8Array;
    ciphertext: Uint8Array;
    tag: Uint8Array;
  };
}

interface MLSGroup {
  groupId: Uint8Array;
  epoch: number;  // Increments on membership changes
  
  members: {
    member: DID;
    leafNode: LeafNode;
  }[];
  
  // Ratchet tree for efficient key updates
  tree: RatchetTree;
  
  // Current group secrets
  secrets: {
    initSecret: Uint8Array;
    senderDataSecret: Uint8Array;
    encryptionSecret: Uint8Array;
    exporterSecret: Uint8Array;
    confirmationKey: Uint8Array;
    membershipKey: Uint8Array;
  };
}

// Sealed sender uses authenticated encryption
// where only the recipient can decrypt

function sealMessage(
  message: Uint8Array,
  recipientPublicKey: Uint8Array
): SealedMessage {
  // Generate ephemeral key pair
  const ephemeral = generateKeypair();
  
  // Compute shared secret
  const shared = x25519(ephemeral.privateKey, recipientPublicKey);
  
  // Derive encryption key
  const key = hkdf(shared, 'sealed-sender');
  
  // Encrypt message
  return {
    ephemeralPublic: ephemeral.publicKey,
    ciphertext: encrypt(key, message),
  };
}

interface PeerAuthentication {
  // Challenge-response protocol
  async authenticate(peer: Peer): Promise<boolean> {
    // 1. Exchange ephemeral keys
    const ephemeral = await exchangeEphemeral(peer);
    
    // 2. Derive session key
    const sessionKey = deriveSessionKey(ephemeral);
    
    // 3. Sign challenge with identity key
    const challenge = randomBytes(32);
    await sendEncrypted(sessionKey, challenge);
    
    // 4. Verify response
    const response = await receiveEncrypted(sessionKey);
    return verifySignature(peer.publicKey, challenge, response);
  }
}

interface RateLimits {
  // Content creation
  postsPerMinute: 10;
  postsPerHour: 100;
  postsPerDay: 500;
  
  // Messaging
  messagesPerMinute: 60;
  conversationsPerDay: 100;
  
  // Network
  connectionsPerMinute: 30;
  queriesPerSecond: 100;
  
  // Reputation-based multipliers
  reputationMultiplier: (reputation: number) => number;
}

interface ProofOfWork {
  challenge: Uint8Array;
  difficulty: number;  // Leading zeros required
  solution: Uint8Array;
  
  verify(): boolean {
    const hash = blake3(concat(this.challenge, this.solution));
    return countLeadingZeros(hash) >= this.difficulty;
  }
}

interface TrafficPadding {
  // Constant rate sending
  sendInterval: 1000;  // ms
  
  // Fixed message size
  maxMessageSize: 16384;  // bytes
  
  // Pad all messages to max
  padMessage(message: Uint8Array): Uint8Array {
    const padded = new Uint8Array(this.maxMessageSize);
    padded.set(message);
    // Random padding for remainder
    crypto.getRandomValues(padded.subarray(message.length));
    return padded;
  }
  
  // Cover traffic when idle
  generateCoverTraffic(): Uint8Array {
    return crypto.getRandomValues(new Uint8Array(this.maxMessageSize));
  }
}

interface ZKProofSystem {
  // Prove membership in a set without revealing which member
  proveMembership(
    set: DID[],
    myIndex: number,
    myKey: PrivateKey
  ): MembershipProof;
  
  // Prove age above threshold without revealing exact age
  proveAgeAbove(
    birthdate: Date,
    threshold: number
  ): RangeProof;
  
  // Prove reputation above threshold
  proveReputationAbove(
    reputation: number,
    threshold: number
  ): RangeProof;
}

// Content validation
function validateContent(input: unknown): ContentObject {
  // Type checking
  if (typeof input !== 'object' || input === null) {
    throw new ValidationError('Invalid content type');
  }
  
  // Required fields
  const required = ['author', 'timestamp', 'payload', 'signature'];
  for (const field of required) {
    if (!(field in input)) {
      throw new ValidationError(`Missing required field: ${field}`);
    }
  }
  
  // Size limits
  if (input.payload.length > MAX_PAYLOAD_SIZE) {
    throw new ValidationError('Payload too large');
  }
  
  // Cryptographic validation
  if (!verifySignature(input)) {
    throw new ValidationError('Invalid signature');
  }
  
  return input as ContentObject;
}

// Secure memory handling
function secureCompare(a: Uint8Array, b: Uint8Array): boolean {
  if (a.length !== b.length) return false;
  
  let result = 0;
  for (let i = 0; i < a.length; i++) {
    result |= a[i] ^ b[i];
  }
  return result === 0;
}

function zeroize(buffer: Uint8Array): void {
  crypto.getRandomValues(buffer);  // Overwrite
  buffer.fill(0);  // Zero
}