HMAC verify

POST /api/hmac-verify1 quota unit per call · cache hits free

Verify an HMAC signature against a payload + secret. Constant-time comparison so timing attacks cannot leak the signature byte-by-byte.

Recomputes an HMAC over the payload + secret and compares it against the signature you supply. Returns `{valid: true}` if they match, `{valid: false}` otherwise. The comparison is constant-time, so an attacker probing for the right signature byte-by-byte cannot use response timing as a side channel. Accepts the signature in hex, standard base64, or URL-safe base64 — same encodings `hmac-sign` produces.

Inputs

Name	Type	Default	Description
data*	string	—	Message that was signed.
secret*	string	—	Shared secret — must match the signer's.
signature*	string	—	Candidate signature to verify.
algorithm	enum (SHA-1 \| SHA-256 \| SHA-384 \| SHA-512)	"SHA-256"	Hash algorithm — must match the signer.
signatureEncoding	enum (hex \| base64 \| base64url)	"hex"	Encoding of the supplied signature.
dataFormat	enum (text \| base64)	"text"	How `data` is encoded. `text` = UTF-8; `base64` for binary.
secretFormat	enum (text \| base64)	"text"	How `secret` is encoded.

Response

Modes: json. Cache: not cacheable.

Every response carries x-cache (HIT / MISS / BYPASS), x-cache-signature (stable across identical inputs), and the rate-limit headers listed below.

Quota & limits

Cost per call	1 unit against the 10,000-unit monthly quota. Cache hits are free — only cache misses decrement.
Burst limit	200 requests per rolling minute, shared across all tools.
Max request size	`16 MiB` (base64 inflates file payloads ~33% — the limit applies to the decoded bytes).
Max response size	`8 KiB`
Timeout	5s wall clock.
Rate-limit headers	`X-RateLimit-Limit`, `X-RateLimit-Remaining`, `X-RateLimit-Burst-Limit` on every response; `X-Quota-Warning` once 80% of the monthly quota is spent; `Retry-After` on 429s.

Errors

Errors are JSON with an error string; schema failures add a details object (Zod's flattened field errors).

Status	When	Body
400	Input fails the tool's schema (wrong type, missing required field, malformed base64) or the file bytes can't be parsed as the expected format.	{ "error": "invalid inputs", "details": { "fieldErrors": { … } } }
401	Missing or invalid X-Api-Key / X-Account-Id headers (or no session when called from the browser).	{ "error": "unauthorized" }
404	Unknown tool id, or calling /api/* on the website hostname instead of api.xtract.bot.	{ "error": "not found" }
413	Request body over the tool's max request size, or an image header declaring more megapixels than the tool's pixel budget.	{ "error": "…exceeds maxRequestBytes…" }
415	Content-Type isn't application/json on the json-body transport.	{ "error": "unsupported content-type; expected application/json" }
429	Monthly quota or the 200/min burst limit exhausted. Check Retry-After and the X-RateLimit-* headers.	{ "error": "monthly quota exceeded", "monthRemaining": 0, … }
5xx	Conversion engine failure. Safe to retry; if it persists, the input is hitting a bug — please report it.	{ "error": "…" }

Code samples

Built from the sha256-known-good example.


curl -X POST https://api.xtract.bot/api/hmac-verify \
  -H "Content-Type: application/json" \
  -H "Accept: application/json" \
  -H "X-Account-Id: $XTRACT_ACCOUNT_ID" \
  -H "X-Api-Key: $XTRACT_API_KEY" \
  -d '{
  "data": "what do ya want for nothing?",
  "secret": "Jefe",
  "signature": "5bdcc146bf60754e6a042426089575c75a003f089d2739839dec58b964ec3843",
  "algorithm": "SHA-256",
  "signatureEncoding": "hex",
  "dataFormat": "text",
  "secretFormat": "text"
}'