Speak Security Basics

Overview

Security best practices for Speak API keys, user data, and audio content in language learning applications.

Prerequisites

Speak SDK installed
Understanding of environment variables
Access to Speak dashboard
Knowledge of audio privacy concerns

Instructions

Step 1: Configure Environment Variables

# .env (NEVER commit to git)
SPEAK_API_KEY=sk_live_***
SPEAK_APP_ID=app_***
SPEAK_WEBHOOK_SECRET=whsec_***

# .gitignore
.env
.env.local
.env.*.local
*.wav  # User audio recordings
*.mp3
recordings/

Step 2: Implement Secret Rotation

# 1. Generate new key in Speak developer dashboard
# https://developer.speak.com/dashboard/api-keys

# 2. Update environment variable
export SPEAK_API_KEY="new_key_here"

# 3. Verify new key works
curl -X POST https://api.speak.com/v1/health \
  -H "Authorization: Bearer ${SPEAK_API_KEY}" \
  -H "X-App-ID: ${SPEAK_APP_ID}"

# 4. Revoke old key in dashboard

Step 3: Apply Least Privilege Access

| Environment | Recommended Scopes | |-------------|-------------------| | Development | lessons:read, speech:analyze | | Staging | lessons:read, lessons:write, speech:analyze | | Production | Only required scopes for features |

// Use scoped API keys per feature
const lessonClient = new SpeakClient({
  apiKey: process.env.SPEAK_LESSON_API_KEY!, // lessons:* only
  appId: process.env.SPEAK_APP_ID!,
});

const speechClient = new SpeakClient({
  apiKey: process.env.SPEAK_SPEECH_API_KEY!, // speech:* only
  appId: process.env.SPEAK_APP_ID!,
});

Step 4: User Audio Privacy

// Audio data handling policies
interface AudioPrivacyConfig {
  retention: 'session_only' | '30_days' | 'permanent';
  shareWithSpeak: boolean; // For model improvement
  allowPlayback: boolean; // Let users hear their recordings
  encryption: 'at_rest' | 'in_transit' | 'both';
}

class SecureAudioHandler {
  private config: AudioPrivacyConfig;

  constructor(config: AudioPrivacyConfig) {
    this.config = config;
  }

  async storeAudio(userId: string, audioData: ArrayBuffer): Promise<string> {
    // Encrypt before storage
    const encrypted = await this.encrypt(audioData);

    // Generate non-guessable ID
    const audioId = crypto.randomUUID();

    // Store with expiration
    const expiry = this.config.retention === 'session_only'
      ? Date.now() + 60 * 60 * 1000 // 1 hour
      : this.config.retention === '30_days'
        ? Date.now() + 30 * 24 * 60 * 60 * 1000
        : null;

    await storage.put(audioId, encrypted, { expiry });

    // Audit log
    await auditLog({
      action: 'audio_stored',
      userId,
      audioId,
      retention: this.config.retention,
    });

    return audioId;
  }

  async deleteUserAudio(userId: string): Promise<void> {
    const audioIds = await storage.listByUser(userId);

    for (const id of audioIds) {
      await storage.delete(id);
    }

    await auditLog({
      action: 'audio_deleted',
      userId,
      count: audioIds.length,
    });
  }

  private async encrypt(data: ArrayBuffer): Promise<ArrayBuffer> {
    // Use AES-256-GCM encryption
    const key = await crypto.subtle.importKey(
      'raw',
      Buffer.from(process.env.AUDIO_ENCRYPTION_KEY!, 'base64'),
      'AES-GCM',
      false,
      ['encrypt']
    );

    const iv = crypto.getRandomValues(new Uint8Array(12));
    const encrypted = await crypto.subtle.encrypt(
      { name: 'AES-GCM', iv },
      key,
      data
    );

    // Prepend IV to encrypted data
    const result = new Uint8Array(iv.length + encrypted.byteLength);
    result.set(iv);
    result.set(new Uint8Array(encrypted), iv.length);

    return result.buffer;
  }
}

Step 5: Webhook Signature Verification

import crypto from 'crypto';

function verifySpeakWebhook(
  payload: string,
  signature: string,
  timestamp: string
): boolean {
  const secret = process.env.SPEAK_WEBHOOK_SECRET!;

  // Reject old timestamps (replay attack protection)
  const timestampAge = Date.now() - parseInt(timestamp) * 1000;
  if (timestampAge > 300000) { // 5 minutes
    console.error('Webhook timestamp too old');
    return false;
  }

  // Compute expected signature
  const signedPayload = `${timestamp}.${payload}`;
  const expectedSignature = crypto
    .createHmac('sha256', secret)
    .update(signedPayload)
    .digest('hex');

  // Timing-safe comparison
  return crypto.timingSafeEqual(
    Buffer.from(signature),
    Buffer.from(`sha256=${expectedSignature}`)
  );
}

// Express middleware
function speakWebhookMiddleware(req: Request, res: Response, next: NextFunction) {
  const signature = req.headers['x-speak-signature'] as string;
  const timestamp = req.headers['x-speak-timestamp'] as string;

  if (!verifySpeakWebhook(req.body.toString(), signature, timestamp)) {
    return res.status(401).json({ error: 'Invalid signature' });
  }

  next();
}

Step 6: User Data Protection

// GDPR/CCPA compliance for language learning data
interface UserLearningData {
  lessonHistory: LessonRecord[];
  pronunciationScores: PronunciationRecord[];
  vocabularyProgress: VocabularyProgress[];
  audioRecordings: AudioReference[];
}

class UserDataManager {
  async exportUserData(userId: string): Promise<UserLearningData> {
    // Gather all user data for GDPR export
    const [lessons, scores, vocab, audio] = await Promise.all([
      db.lessons.findByUser(userId),
      db.pronunciation.findByUser(userId),
      db.vocabulary.findByUser(userId),
      storage.listAudioByUser(userId),
    ]);

    await auditLog({
      action: 'user_data_export',
      userId,
      timestamp: new Date(),
    });

    return {
      lessonHistory: lessons,
      pronunciationScores: scores,
      vocabularyProgress: vocab,
      audioRecordings: audio,
    };
  }

  async deleteUserData(userId: string): Promise<DeletionResult> {
    // Complete data deletion for GDPR
    const results = await Promise.allSettled([
      db.lessons.deleteByUser(userId),
      db.pronunciation.deleteByUser(userId),
      db.vocabulary.deleteByUser(userId),
      this.deleteUserAudio(userId),
      speakClient.users.delete(userId), // Delete from Speak's servers
    ]);

    await auditLog({
      action: 'user_data_deleted',
      userId,
      timestamp: new Date(),
      results: results.map(r => r.status),
    });

    return {
      success: results.every(r => r.status === 'fulfilled'),
      timestamp: new Date(),
    };
  }
}

Security Checklist

API Security

[ ] API keys in environment variables
[ ] .env files in .gitignore
[ ] Different keys for dev/staging/prod
[ ] Minimal scopes per environment
[ ] Webhook signatures validated
[ ] Key rotation schedule documented

Audio Security

[ ] Audio encrypted at rest
[ ] Audio encrypted in transit (HTTPS)
[ ] Clear retention policy
[ ] User consent obtained
[ ] Deletion mechanism implemented

User Data

[ ] GDPR export implemented
[ ] CCPA compliance verified
[ ] Audit logging enabled
[ ] Data minimization practiced
[ ] Privacy policy updated

Output

Secure API key storage
Environment-specific access controls
Audio privacy protection
Webhook security enabled
User data protection compliance

Error Handling

| Security Issue | Detection | Mitigation | |----------------|-----------|------------| | Exposed API key | Git scanning, audit logs | Rotate immediately | | Excessive scopes | Audit logs review | Reduce permissions | | Missing rotation | Key age check | Schedule rotation | | Audio leak | Access logs | Encrypt and restrict | | Missing consent | Compliance audit | Update consent flow |

Examples

Service Account Pattern

const clients = {
  lessons: new SpeakClient({
    apiKey: process.env.SPEAK_LESSON_KEY,
    appId: process.env.SPEAK_APP_ID,
  }),
  speech: new SpeakClient({
    apiKey: process.env.SPEAK_SPEECH_KEY,
    appId: process.env.SPEAK_APP_ID,
  }),
};

Audit Logging

interface AuditEntry {
  timestamp: Date;
  action: string;
  userId: string;
  resource: string;
  result: 'success' | 'failure';
  metadata?: Record<string, any>;
}

async function auditLog(entry: Omit<AuditEntry, 'timestamp'>): Promise<void> {
  const log: AuditEntry = { ...entry, timestamp: new Date() };

  // Store in audit database
  await auditDb.insert(log);

  // Also log for compliance
  console.log('[AUDIT]', JSON.stringify(log));
}

Resources

Next Steps

For production deployment, see speak-prod-checklist.