HashOnClick: Quick Setup and Best PracticesHashOnClick is a small client-side library that computes cryptographic hashes (SHA-256, SHA-1, MD5, etc.) directly in the browser when a user clicks a button or submits a form. It’s useful for hashing emails, passwords, or other sensitive values before sending them to a server, for generating unique identifiers, or for adding a lightweight integrity check. This article covers a quick setup, integration examples, configuration options, and best practices to use HashOnClick safely and effectively.
Why use client-side hashing?
- Reduce exposure of raw sensitive values: hashing in the browser prevents the original value (e.g., email or password) from being sent in plaintext across the network.
- Consistent client-side identifiers: when you need a stable, deterministic identifier derived from input that isn’t reversible, hashing can work well.
- Lightweight integrity checks: quick checksums can detect accidental changes to data before uploading.
Note: client-side hashing is not a replacement for proper server-side security. Hashing before transmission can improve privacy but doesn’t eliminate the need for server-side hashing/salting, transport encryption (HTTPS), and secure storage.
Quick setup
1) Include HashOnClick in your project
If HashOnClick is distributed as a standalone JS file, include it via a script tag:
<script src="path/to/hashonclick.min.js"></script> Or install via npm/yarn if available:
npm install hashonclick # or yarn add hashonclick Then import it in your bundle:
import HashOnClick from 'hashonclick'; 2) Minimal HTML example
<form id="signup"> <input id="email" name="email" type="email" required /> <input id="password" name="password" type="password" required /> <button id="hashBtn" type="button">Hash & Submit</button> </form> 3) Hook it up with minimal JavaScript
const btn = document.getElementById('hashBtn'); const form = document.getElementById('signup'); btn.addEventListener('click', async () => { // HashOnClick API example (pseudo-API) await HashOnClick.hashField({ form, fieldName: 'password', algorithm: 'SHA-256', outputFieldName: 'password_hash' }); // Optionally hash email await HashOnClick.hashField({ form, fieldName: 'email', algorithm: 'SHA-256', outputFieldName: 'email_hash' }); form.submit(); }); This example assumes HashOnClick provides a hashField utility that takes a form, a field to read, the algorithm, and a name for the output field. If the library exposes a different API, adjust accordingly.
Common configuration options
- algorithm: ‘SHA-256’ | ‘SHA-1’ | ‘MD5’ | custom — choose a modern algorithm; prefer SHA-256 or stronger.
- salt: string | function — optional salt to combine with the input before hashing. A function can add per-input randomness (timestamp, device ID).
- iterations: number — repeat hashing N times (key stretching) to slow brute-force of weak inputs.
- outputFormat: ‘hex’ | ‘base64’ — encoding format of the hash.
- replaceField: boolean — whether to replace the original field value or add a new hidden field with the hash. Prefer adding a new field.
- omitEmpty: boolean — skip hashing when the source field is empty.
Integration patterns
Replace vs. add hidden field
- Replace original value: less data sent, but you lose the original on the client if needed later.
- Add hidden field: safer for debugging and avoids losing client-side state; remove or disable the original field before submission if you want to avoid sending both.
Example: add hidden field
async function addHashField(form, sourceName, hashName, opts) { const source = form.elements[sourceName]; const value = source.value || ''; const hash = await HashOnClick.compute(value, opts); let hidden = form.querySelector(`input[name="${hashName}"]`); if (!hidden) { hidden = document.createElement('input'); hidden.type = 'hidden'; hidden.name = hashName; form.appendChild(hidden); } hidden.value = hash; // Optionally disable original: // source.disabled = true; } Progressive enhancement
Bind HashOnClick to click events on buttons, but allow normal form submission when JavaScript is disabled. Ensure server accepts either hashed or raw values or degrades gracefully.
Security best practices
- Always use HTTPS. Hashing in the browser does not replace TLS.
- Treat client-side hashes as potentially observable secrets. Use them as mitigations for privacy, not as the only authentication mechanism.
- On the server, still apply proper password hashing (bcrypt/scrypt/Argon2) with unique salts. Client-side hashing can be a pre-hash step but should never be the sole line of defense.
- Avoid using fast, broken algorithms (MD5, SHA-1) for security-critical contexts. Use SHA-256 or better.
- If hashing passwords, prefer key-stretching on the server (Argon2/bcrypt). If you pre-hash on the client, combine that with server-side salting and slow hashing.
- Be careful with deterministic hashes for identifiers: two users with the same email will produce the same hash. If uniqueness is required across systems, include a namespace salt.
- Do not rely on client-side hashing to prevent server-side logging of identifiers. Assume the server will see whatever you send and architect privacy accordingly.
Performance considerations
- Hashing is CPU work—on low-end devices or large inputs it may block the main thread. Use Web Workers for heavy tasks or large iteration counts.
- Prefer streaming APIs (when available) for very large inputs to reduce memory pressure.
- Keep iteration counts reasonable for client devices; heavy stretching should be done server-side.
Example: using Web Crypto API (vanilla JS)
If HashOnClick is not used or you want to implement hashing yourself:
async function sha256Hex(str) { const enc = new TextEncoder(); const data = enc.encode(str); const hash = await crypto.subtle.digest('SHA-256', data); const bytes = new Uint8Array(hash); return Array.from(bytes).map(b => b.toString(16).padStart(2, '0')).join(''); } This uses the browser’s built-in Web Crypto API for fast, secure hashing.
Testing and debugging
- Test across browsers and devices, especially mobile, to ensure hashing completes quickly and reliably.
- Log intermediate steps in development (never log sensitive values in production).
- Use unit tests to verify consistent outputs for given inputs and configuration.
When not to use client-side hashing
- When you need true authentication relying on server-side hashing schemes (always do server-side verification).
- When you need irreversible, server-controlled salting and stretching.
- When the library causes unacceptable latency on low-powered devices.
Conclusion
HashOnClick can be a simple, effective privacy and utility tool when used appropriately: include it, bind to user actions, choose modern algorithms, avoid replacing server-side security, and consider performance on real devices. Use the browser’s Web Crypto API for secure, fast hashing and push heavy work to the server when necessary.
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