scrypt derive

POST /api/scrypt-derive4 quota units per call · cache hits free

Stretch a password into a key with scrypt — the memory-hard KDF from RFC 7914. Configurable N (cost), r (block size), p (parallelisation), and output length. Returns hex / base64 / base64url.

Stretches a password into a cryptographic key with scrypt — a **memory-hard** KDF specified in RFC 7914. Unlike PBKDF2, scrypt deliberately consumes large amounts of memory per derivation, which dramatically raises the cost of an attacker using ASICs or GPUs. Parameters (interactive-login defaults shown): - `N`: CPU/memory cost (power of 2, default 16384 = 2¹⁴). - `r`: block size in 128-byte chunks (default 8). - `p`: parallelisation factor (default 1). - Memory cost ≈ 128 · N · r bytes. The defaults use ~16 MB. Recommended for password storage when you control both ends of the verification. For interop with non-scrypt systems, prefer `pbkdf2-derive`.

Inputs

Name	Type	Default	Description
password*	string	—	Password to stretch.
salt*	string	—	Per-user salt (≥16 bytes recommended).
N	number (2…1048576)	16384	CPU/memory cost. Must be a power of 2.
r	number (1…32)	8	Block size in 128-byte chunks.
p	number (1…16)	1	Parallelisation factor.
bitsLength	number (8…4096)	256	Output key length in bits.
passwordFormat	enum (text \| hex \| base64)	"text"	Input encoding of `password`.
saltFormat	enum (text \| hex \| base64)	"text"	Input encoding of `salt`.
outputFormat	enum (hex \| base64 \| base64url)	"hex"	Output encoding of the derived key.

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	4 units 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	`64 KiB` (base64 inflates file payloads ~33% — the limit applies to the decoded bytes).
Max response size	`16 KiB`
Timeout	60s 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 default example.


curl -X POST https://api.xtract.bot/api/scrypt-derive \
  -H "Content-Type: application/json" \
  -H "Accept: application/json" \
  -H "X-Account-Id: $XTRACT_ACCOUNT_ID" \
  -H "X-Api-Key: $XTRACT_API_KEY" \
  -d '{
  "password": "correct horse battery staple",
  "salt": "xtract.bot-demo-salt",
  "N": 16384,
  "r": 8,
  "p": 1,
  "bitsLength": 256,
  "outputFormat": "hex"
}'