ForHosting KIT · Developer Utilities

Book cipher

A book cipher hides a short message by pointing at words that already exist in a shared passage instead of inventing a substitution alphabet.

● BetaFree · in your browser

Run — free How it works & API

Use it from WebAPIEmailTelegramApp soon

Paste any key text you and your counterpart both hold—a paragraph, a poem, or a printed page—then encrypt a phrase into a list of 1-based word positions, or decrypt those numbers back into the original words. Matching is case-insensitive, leading and trailing punctuation is stripped during tokenization, and any message words that do not appear in the key are listed so you can extend the passage or rephrase the plaintext. The engine is pure and deterministic: the same key and message always yield the same positions, with no network calls, random seeds, or clocks. Use it free in the browser for classroom demos and puzzle design, or call the identical logic through the API at $0.002 per successful request.

How to use it

Enter your values in the form above. The tool checks them before calculating and shows the result on the same page.

Check your inputs

Use the labels and units shown next to each field. If something is missing or outside the allowed range, the page points to the field to fix.

Use it again or automate it

Use the browser tool for individual checks and the API when you need the same capability in an automated workflow.

What you can do with it

Get an answer now

Enter one set of values and see the result without building a spreadsheet or script.

Compare scenarios

Change one value at a time and rerun the calculation to understand what affects the result.

Automate repeated work

Use the API when the same calculation needs to run inside your product or workflow.

FAQ

How do I use this capability?

Complete the fields above and run it on this page. The form highlights anything that needs attention.

For developers — API access

Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.

API endpoint

POSThttps://api.kit.forhosting.com/enc/book-cipher

Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.

Call it from your stack

curl -X POST https://api.kit.forhosting.com/enc/book-cipher \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"key_text":"The quick brown fox jumps over the lazy dog near the river bank","message":"quick fox river"}'

const res = await fetch("https://api.kit.forhosting.com/enc/book-cipher", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "key_text": "The quick brown fox jumps over the lazy dog near the river bank",
    "message": "quick fox river"
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/enc/book-cipher",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "key_text": "The quick brown fox jumps over the lazy dog near the river bank",
    "message": "quick fox river"
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/enc/book-cipher", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"key_text":"The quick brown fox jumps over the lazy dog near the river bank","message":"quick fox river"}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"key_text":"The quick brown fox jumps over the lazy dog near the river bank","message":"quick fox river"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/enc/book-cipher", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "key_text": "The quick brown fox jumps over the lazy dog near the river bank",
  "message": "quick fox river"
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "enc.book_cipher",
  "status": "queued",
  "_links": {
    "result": "/tasks/tsk_…/result"
  }
}

The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.

Pricing

Per request$0.002

Published price — no tokens, no invented credits. A failed task is never charged.

Errors

HTTP	Code	Meaning
`401`	`unauthorized`	Missing or invalid API key.
`402`	`insufficient_balance`	Your balance doesn't cover the task price.
`404`	`unknown_type`	That task type doesn't exist.
`429`	`rate_limited`	Too many requests. Use the webhook instead of polling.

Read the full KIT documentation →