castomAPI
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POST /v1/crypto/encrypt free No key needed Crypto

Encrypt plaintext using AES-256-GCM with auto-generated IV

Encrypt plaintext using AES-256-GCM with auto-generated IV, authentication tag, and optional scrypt key derivation

POST

Request

  • x-api-key: <your-api-key>
  • Content-Type: application/json

Response 

{
  "algorithm": "<algorithm>",
  "associatedDataProvided": true,
  "ciphertext": "<ciphertext>",
  "iv": "<iv>",
  "keyDerivation": {
    "kdf": "<kdf>",
    "keyLengthBits": 22,
    "salt": "<salt>"
  },
  "outputEncoding": "utf-8",
  "status": "success",
  "tag": "<tag>",
  "tokensDeducted": 1
}
The response below is a mock built from the endpoint's own schema — no request leaves this page. Edit the body, press Send, read the shape you will get back. Run it for real in the dashboard →

What it does

Encrypt plaintext using AES-256-GCM with auto-generated IV, authentication tag, and optional scrypt key derivation

Request

Body

FieldTypeRequiredDescription
associatedDatastringnoOptional Additional Authenticated Data (AAD) bound to the GCM auth tag.
keystringno32-byte key formatted in hex (64 chars), base64 (44 chars), or raw string.
keyEncodingenumnoOne of: hex, base64, utf8.
outputEncodingenumnoOne of: hex, base64, base64url.
passphrasestringnoOptional passphrase used to derive a 256-bit key via scrypt if no raw key is supplied.
plaintextstringyes

Example request

{
  "associatedData": "<associated data>",
  "key": "example",
  "keyEncoding": "hex",
  "outputEncoding": "hex",
  "passphrase": "<passphrase>",
  "plaintext": "<plaintext>"
}

Response

FieldTypeDescription
algorithmstring
associatedDataProvidedboolean
ciphertextstring
ivstring
keyDerivationobject
  ↳ kdfstring
  ↳ keyLengthBitsinteger
  ↳ saltstring
outputEncodingstring
statusstring
tagstring
tokensDeductedinteger

Example response

{
  "algorithm": "<algorithm>",
  "associatedDataProvided": true,
  "ciphertext": "<ciphertext>",
  "iv": "<iv>",
  "keyDerivation": {
    "kdf": "<kdf>",
    "keyLengthBits": 22,
    "salt": "<salt>"
  },
  "outputEncoding": "utf-8",
  "status": "success",
  "tag": "<tag>",
  "tokensDeducted": 1
}

Errors

Every error answers with the same envelope: an HTTP status, a machine code and a sentence.

400The body or a parameter failed validation. The details array names the field.
401No key, a revoked key or a wrong header. Send x-api-key.
402The wallet cannot cover this call. Top up or wait for the monthly grant.
404The resource does not exist, or it is not yours. Both answer identically and cost nothing.
429Over the per-minute quota of your tier. Back off and retry.
5xxUpstream refused or timed out. The call is not billed.

Code

curl -X POST 'https://app.castomapi.com/v1/crypto/encrypt' \
  -H 'x-api-key: <your-api-key>' \
  -H 'Content-Type: application/json' \
  -d '{"associatedData": "<associated data>", "key": "example", "keyEncoding": "hex", "outputEncoding": "hex", "passphrase": "<passphrase>", "plaintext": "<plaintext>"}'
const res = await fetch('https://app.castomapi.com/v1/crypto/encrypt', {
  method: 'POST',
  headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
  body: JSON.stringify({"associatedData": "<associated data>", "key": "example", "keyEncoding": "hex", "outputEncoding": "hex", "passphrase": "<passphrase>", "plaintext": "<plaintext>"})
});
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/crypto/encrypt', {
  method: 'POST',
  headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
  body: JSON.stringify({"associatedData": "<associated data>", "key": "example", "keyEncoding": "hex", "outputEncoding": "hex", "passphrase": "<passphrase>", "plaintext": "<plaintext>"})
});
const data = await res.json();
console.log(data);
import requests

res = requests.post(
    'https://app.castomapi.com/v1/crypto/encrypt',
    headers={'x-api-key': '<your-api-key>'},
    json={"associatedData": "<associated data>", "key": "example", "keyEncoding": "hex", "outputEncoding": "hex", "passphrase": "<passphrase>", "plaintext": "<plaintext>"},
    timeout=30,
)
print(res.json())
<?php
$ch = curl_init('https://app.castomapi.com/v1/crypto/encrypt');
curl_setopt_array($ch, [
    CURLOPT_CUSTOMREQUEST => 'POST',
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['x-api-key: <your-api-key>', 'Content-Type: application/json'],
    CURLOPT_POSTFIELDS => json_encode(['associatedData' => '<associated data>', 'key' => 'example', 'keyEncoding' => 'hex', 'outputEncoding' => 'hex', 'passphrase' => '<passphrase>', 'plaintext' => '<plaintext>']),
]);
$data = json_decode(curl_exec($ch), true);
print_r($data);

Cost and limits

This operation needs no API key and costs nothing: called without a key it answers 200 and deducts zero tokens, up to 10 requests a minute per IP address.

Rate limits per minute

No key10
Free60
Pro300
Enterprise1200

Docs → Pricing

Questions

What does Encrypt plaintext using AES-256-GCM with auto-generated IV cost?

This operation needs no API key and costs nothing: called without a key it answers 200 and deducts zero tokens, up to 10 requests a minute per IP address.

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