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The Secure Key-based Signing Utility is a fully client-side browser tool that lets you create HMAC-SHA256 message authentication codes (MACs) using a secret key or passphrase you control. It is designed for freelancers, crypto users, consultants, and individuals in Pakistan who need a simple, private way to prove message authenticity and integrity — such as confirming payment approvals, milestone acceptances, document handovers, or off-chain agreements — without relying on blockchain wallets, certificates, or external services.
Enter your message (e.g. approval text, invoice confirmation, delivery acknowledgment), provide a strong secret key/passphrase (never stored or sent), and click "Sign with Key". The tool computes an HMAC-SHA256 tag using the Web Crypto API, then produces a copyable block containing the original message, timestamp (PKT), key-derived tag (hex), and reference details. Anyone with the same secret key can later re-compute the HMAC and verify the message has not been altered. The output is ideal for pasting into WhatsApp, email threads, Notion, Google Docs, or client chats as a lightweight proof of origin and integrity.
All computation happens locally in your browser — the secret key never leaves your device, no data is uploaded, and nothing is stored. It is especially useful for scenarios where full public-key cryptography (like Ethereum signatures) is unnecessary or too complex, yet you still want cryptographic assurance stronger than plain text. The tool is mobile-friendly, works offline after loading, and emphasizes security best practices (key never saved, HMAC resistant to length-extension attacks).
Use it daily to add verifiable authenticity to freelance communications, crypto-related agreements, or internal records — fast, private, zero-cost, and cryptographically strong. Perfect when trust and proof matter but blockchain isn’t required. (Word count ≈ 302)