Check candidate passwords against breach databases
Check candidate passwords against breach databases using NIST 800-63B compliant k-Anonymity SHA-1 prefix hashing. The raw password is never transmitted or logged
Request
- x-api-key: <your-api-key>
- Content-Type: application/json
Response
{
"breachCount": 3,
"isCompromised": true,
"nist80063bCompliant": true,
"securityAudit": {
"kAnonymityPreserved": true,
"paddedResponse": true,
"recommendation": "<recommendation>",
"sha1Prefix": "<sha1 prefix>"
},
"status": "success",
"tokensDeducted": 1
}What it does
Check candidate passwords against breach databases using NIST 800-63B compliant k-Anonymity SHA-1 prefix hashing. The raw password is never transmitted or logged
Request
Body
| Field | Type | Required | Description |
|---|---|---|---|
password | string | yes | The plain-text candidate password string to audit. |
Example request
{
"password": "correct-horse-battery-staple"
}Response
| Field | Type | Description |
|---|---|---|
breachCount | integer | |
isCompromised | boolean | |
nist80063bCompliant | boolean | |
securityAudit | object | |
↳ kAnonymityPreserved | boolean | |
↳ paddedResponse | boolean | |
↳ recommendation | string | |
↳ sha1Prefix | string | |
status | string | |
tokensDeducted | integer |
Example response
{
"breachCount": 3,
"isCompromised": true,
"nist80063bCompliant": true,
"securityAudit": {
"kAnonymityPreserved": true,
"paddedResponse": true,
"recommendation": "<recommendation>",
"sha1Prefix": "<sha1 prefix>"
},
"status": "success",
"tokensDeducted": 1
}Errors
Every error answers with the same envelope: an HTTP status, a machine code and a sentence.
400 | The body or a parameter failed validation. The details array names the field. |
401 | No key, a revoked key or a wrong header. Send x-api-key. |
402 | The wallet cannot cover this call. Top up or wait for the monthly grant. |
404 | The resource does not exist, or it is not yours. Both answer identically and cost nothing. |
429 | Over the per-minute quota of your tier. Back off and retry. |
5xx | Upstream refused or timed out. The call is not billed. |
Code
curl -X POST 'https://app.castomapi.com/v1/verify/password-breach' \
-H 'x-api-key: <your-api-key>' \
-H 'Content-Type: application/json' \
-d '{"password": "correct-horse-battery-staple"}'const res = await fetch('https://app.castomapi.com/v1/verify/password-breach', {
method: 'POST',
headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
body: JSON.stringify({"password": "correct-horse-battery-staple"})
});
const data = await res.json();
console.log(data);import { request } from 'node:https';
// Node 18+ has fetch built in
const res = await fetch('https://app.castomapi.com/v1/verify/password-breach', {
method: 'POST',
headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
body: JSON.stringify({"password": "correct-horse-battery-staple"})
});
const data = await res.json();
console.log(data);import requests
res = requests.post(
'https://app.castomapi.com/v1/verify/password-breach',
headers={'x-api-key': '<your-api-key>'},
json={"password": "correct-horse-battery-staple"},
timeout=30,
)
print(res.json())<?php
$ch = curl_init('https://app.castomapi.com/v1/verify/password-breach');
curl_setopt_array($ch, [
CURLOPT_CUSTOMREQUEST => 'POST',
CURLOPT_RETURNTRANSFER => true,
CURLOPT_HTTPHEADER => ['x-api-key: <your-api-key>', 'Content-Type: application/json'],
CURLOPT_POSTFIELDS => json_encode(['password' => 'correct-horse-battery-staple']),
]);
$data = json_decode(curl_exec($ch), true);
print_r($data);Cost and limits
This operation costs 1 token. A call that fails is never billed. Every account gets 1000 free tokens a month; paid balances never expire.
Rate limits per minute
| No key | 10 |
| Free | 60 |
| Pro | 300 |
| Enterprise | 1200 |
Questions
What does Check candidate passwords against breach databases cost?
1 token per successful call, debited from your wallet after the response. Failed calls are free. Every account receives 1000 free tokens a month.
How do I authenticate?
Send your key in the x-api-key header. One key covers every metered endpoint; there is nothing to enable per endpoint.
Can I send an Authorization: Bearer token instead?
Not for a metered endpoint — those take the x-api-key header and nothing else. Bearer tokens belong to the account side: the dashboard and account APIs accept a JWT session, and castomapi-auth issues those through a standard OAuth2 handshake, with authorization code, client credentials and refresh grants. The auth service page covers it.
What are the limits?
10 requests a minute per IP with no key at all, 60 a minute on the free tier, 300 on Pro, 1200 on Enterprise. Above the no-key tier the quota is per account, across every endpoint.
OpenAPI: https://app.castomapi.com/docs/json