HMAC Generator
Calculate cryptographically signed Hash-Based Message Authentication Codes (HMAC) using SHA-256, SHA-512, and secret keys compliant with RFC 2104.
Quick Answer & Understanding Your Result
An HMAC Generator calculates cryptographic Hash-Based Message Authentication Codes (HMAC) adhering to IETF RFC 2104, using secret keys combined with SHA-256, SHA-512, SHA-1, or MD5 hash functions.
Core HMAC Cryptographic Principles (RFC 2104)
- Shared Secret Key Signing: Verifies both data integrity and message authenticity simultaneously between two communicating parties.
- Multi-Algorithm Support: Calculates HMAC-SHA256, HMAC-SHA512, HMAC-SHA1, and HMAC-MD5.
- Web & Payment Webhook Standard: The industry-standard signature scheme used by Stripe, GitHub Webhooks, AWS Signature v4, and PayPal.
API & Payment Security Applications
- Payment Gateway Webhook Verification: Verifying incoming webhook signatures from Stripe (
Stripe-Signature) and PayPal. - API Request Signing (AWS SigV4): Generating cryptographically signed authentication headers for cloud APIs.
Enter message payload and secret key above to generate your HMAC signature instantly.
Formula & Calculation Logic
Technical Specification & ASTRFC 2104 HMAC construction:
- Hashes key XOR inner padding (0x36) concatenated with message, followed by outer hash with key XOR outer padding (0x5C).
Step-by-Step Guide
Enter Message Payload
Paste text or JSON webhook payload into the message box.
Enter Secret Key & Choose Algorithm
Input shared secret key and select HMAC-SHA256 or HMAC-SHA512.
Copy HMAC Signature
Copy generated hex signature for Authorization or Webhook headers.
Worked Examples Table
| Example | Input Values | Calculated Result | Explanation |
|---|---|---|---|
| HMAC-SHA256 Signature | Calculated HMAC-SHA256 signature using shared secret. | ||
| GitHub Webhook Signature | Provides instant quantitative evaluation for comparative practical analysis. |
Frequently Asked Questions
Evidence-Based Methodology & Authoritative References
IETF RFC 2104 - HMAC: Keyed-Hashing for Message Authentication
NIST FIPS PUB 198-1 - The Keyed-Hash Message Authentication Code (HMAC)
Standard: ISO / W3C / IETF Authoritative Domain Standard
Formula: HMAC(K, m) = H((K' oplus opad) mathbinVert H((K' oplus ipad) mathbinVert m))
Last Reviewed: August 21, 2026
Primary Source: IETF RFC 2104 - HMAC: Keyed-Hashing for Message Authentication
Reference Document: NIST FIPS PUB 198-1 - The Keyed-Hash Message Authentication Code (HMAC)
Computation Privacy: 100% client-side 0ms computation, zero data retention
All algorithms, formatters, and data conversions run 100% locally in your browser following official technical standards (RFC, ISO, W3C). Output should be verified prior to mission-critical production deployment.
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Calculated results are modeled based on standard scientific and mathematical formulas. Please verify with domain-specific technical documentation for specialized applications.