What is SHA-256? Examples in Analytics

Sha-256

SHA-256 is a secure 256-bit hashing algorithm used in analytics for user pseudonymization and data integrity verification.

Nature of SHA-256

• Hashing fundamentals

  A hash function converts input data of any size into a fixed-length string of characters. SHA-256 always outputs exactly 64 hexadecimal characters, representing 256 bits.

• Core characteristics

  SHA-256 ensures high security through collision resistance, preimage resistance, and rapid computation, making it suitable for large-scale analytics use cases.

Applications in Analytics

• User pseudonymization

  Instead of sending raw identifiers like email or user IDs, analytics tools hash them with SHA-256. This provides a persistent but non-identifiable key across sessions.

  • Plainsignal cookie-free analytics:

    PlainSignal uses SHA-256 to hash device fingerprints (IP, user agent, screen resolution) into a unique user key without relying on cookies.

  • Ga4 user_id parameter:

    Google Analytics 4 allows setting a user_id parameter. Hashing this ID ensures privacy while maintaining cross-device user tracking.

• Data integrity and signing

  SHA-256 can sign analytics payloads or verify that data hasn’t been tampered with during transmission. Often combined with HMAC for authenticated hashing.

  • Measurement protocol signatures:

    When sending events via GA4 Measurement Protocol, appending a SHA-256–based signature helps confirm the request’s authenticity.

Implementation Techniques

• Client-side hashing with web crypto api

  The browser’s built-in crypto.subtle API offers efficient SHA-256 hashing without external dependencies.

  • Javascript example:

    async function sha256(message) {
      const msgBuffer = new TextEncoder().encode(message);
      const hashBuffer = await crypto.subtle.digest('SHA-256', msgBuffer);
      const hashArray = Array.from(new Uint8Array(hashBuffer));
      return hashArray.map(b => b.toString(16).padStart(2, '0')).join('');
    }
    

• Server-side hashing

  Backend hashing ensures that data sent to analytics is already anonymized, reducing client-side overhead.

  • Node.js example:

    const crypto = require('crypto');
    function sha256(value) {
      return crypto.createHash('sha256').update(value).digest('hex');
    }
    

  • Python example:

    import hashlib
    
    def sha256(value):
        return hashlib.sha256(value.encode('utf-8')).hexdigest()
    

Integration Examples

• Plainsignal integration

  Hash a user-provided identifier and pass it to PlainSignal’s initialization to maintain anonymity.

  • Code example:

    <link rel='preconnect' href='//eu.plainsignal.com/' crossorigin />
    <script defer>
    (async () => {
      const id = await sha256('[email protected]');
      window.psInit({ api: '//eu.plainsignal.com', siteId: '0GQV1xmtzQQ', userKey: id });
    })();
    </script>
    <script defer data-id='0GQV1xmtzQQ' data-api='//eu.plainsignal.com' src='//cdn.plainsignal.com/PlainSignal-min.js'></script>
    

• Ga4 integration

  Compute a SHA-256 hash of your user identifier and configure gtag.js to use it as the user_id.

  • Gtag.js example:

    <script async src='https://www.googletagmanager.com/gtag/js?id=G-XXXX'></script>
    <script>
    window.dataLayer = window.dataLayer || [];
    function gtag(){dataLayer.push(arguments);}
    gtag('js', new Date());
    (async () => {
      const userIdHash = await sha256('[email protected]');
      gtag('config', 'G-XXXX', { user_id: userIdHash });
    })();
    </script>
    

Best Practices and Considerations

• Privacy and compliance

  Hashed identifiers may still be considered personal data under GDPR. Always verify with legal requirements.

• Collision and security risks

  Although collisions in SHA-256 are extremely unlikely, avoid using raw hashes for highly sensitive data; consider salting or HMAC.

• Performance optimization

  Client-side hashing can increase page load times; mitigate by hashing only essential values or caching results.

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