HMAC Signature Generator
Compute Hash-based Message Authentication Codes (HMAC) using SHA-256 or SHA-512 securely on the client-side.
What is an HMAC (Keyed-Hash Message Authentication Code)?
An **HMAC** is a cryptographic constructor that combines a cryptographic hash function with a secret key. Unlike simple hash functions (like MD5 or SHA-256 alone) which are prone to length extension attacks if used as MACs, the HMAC protocol processes the secret key and the message twice to ensure robustness.
Its primary security property is that it is computationally impossible to construct a matching signature for a message without having access to the secret key, even if you know the message contents and the signing algorithm.
Standard Use Cases for HMAC Digests
HMAC signatures are heavily used in modern software architectures:
- API Webhook Validation: Slack, Stripe, and GitHub sign webhook payload bodies using an HMAC-SHA256 signature, which their consumers verify locally to validate the message originated from them.
- AWS API Authorization: Amazon Web Services uses HMAC keys to sign request queries (Signature Version 4) to validate AWS credentials securely.
Frequently Asked Questions
An HMAC (Keyed-Hash Message Authentication Code) is a specific type of message authentication code involving a cryptographic hash function and a secret cryptographic key. It is used to simultaneously verify both the data integrity and the authenticity of a message.
Yes. Instead of using third-party JavaScript libraries, this tool utilizes the browser's built-in Web Crypto API (SubtleCrypto.sign) which performs calculations securely and extremely fast at native execution speeds.
No. The calculation process occurs locally inside your browser sandbox. The secret key is never sent over HTTP request streams, protecting your web hooks and API secret keys.