Encoding and decoding
HMAC Generator/Verifier
Authenticate a pasted message or local file with an HMAC key in your browser.
Processed locally. Your input and output are never uploaded.
Tool overview
How HMAC Generator/Verifier works
HMAC Generator/Verifier uses Web Crypto to sign the current input with a local key and optionally compares the tag with an expected value. It keeps input and output separate, runs locally, and documents boundaries instead of making unsupported guarantees.
Message authentication test vectors
- uses Web Crypto to sign the current input with a local key and optionally compares the tag with an expected value. for a repeatable local workflow
- Review pasted or locally opened data before copying it
- Prepare output for a related PasteTidy tool
Sign a message with a local key
- Paste the source or open a supported local file.
- Choose the documented options and review the separate result.
- Copy or download only after checking the visible output.
Key encoding and tag comparison
- Algorithm: HMAC hash function.
- Key: Key value used only for this operation.
- Key encoding: Interpretation of key text.
- Output encoding: Text encoding for the tag.
- Expected tag: Optional HMAC tag to verify.
Generate an HMAC tag
Before
message
After
{
"algorithm": "HMAC-SHA-256",
"digest": "8b5f48702995c1598c573db1e21866a9b825d4a794d169d7060a03605796360b"
}Secrets and authentication boundaries
- Ambiguous or malformed input is reported instead of silently repaired.
- Large input is bounded by the documented local worker limits.
- Input, options, and output are not sent to analytics or placed in URLs.
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Questions
HMAC Generator/Verifier FAQ
Does HMAC Generator/Verifier upload my input?
No. Processing stays in the current browser tab or its local Web Worker.
Is the result authoritative?
No. Review the output and the documented limitations before using it in a production workflow.