Frequency Analysis

{
  "asOf": "2026-10-11T14:31:57.586Z",
  "candidatePlaintext": "This is a secret message about a caesar cipher with a funny shift",
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "englishIC": 0.0667,
  "frequencies": [
    {
      "count": 0,
      "englishPercent": 8.167,
      "letter": "A",
      "percent": 0
    },
    {
      "count": 1,
      "englishPercent": 1.492,
      "letter": "B",
      "percent": 1.8868
    }
  ],
  "indexOfCoincidence": 0.0668,
  "interpretation": "single-alphabet text (plain English or a Caesar/substitution cipher of it)",
  "letters": 53,
  "likelyShift": 3,
  "mostCommon": [
    "D 13.2075%",
    "V 13.2075%",
    "…3 more"
  ],
  "notChecked": [
    "languages other than English (the shift guess assumes English letter frequencies)",
    "texts under about 40 letters, where statistics are unreliable",
    "…1 more"
  ],
  "randomIC": 0.0385,
  "reasons": [
    "English text has an index of coincidence near 0.066; random letters near 0.038.",
    "The shift guess minimises the chi-squared distance from English letter frequencies; confidence is the ratio of the runner-up's distance to the best."
  ],
  "runnerUpShift": 16,
  "shiftConfidenceRatio": 8.66,
  "source": "computed locally (Lewand English letter frequencies, Friedman index of coincidence)",
  "summary": "IC 0.0668; most likely Caesar shift 3 (decode with shift -3). Most common: D 13.2075%, V 13.2075%, H 11.3208%, L 9.434%, W 9.434%.",
  "verdict": "LIKELY_CAESAR_SHIFT"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://text-ciphers.x402tookit.com/frequency-analysis?text=Wklv+lv+d+vhfuhw+phvvdjh+derxw+d+fdhvdu+flskhu+zlwk+d+ixqqb+vkliw'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://text-ciphers.x402tookit.com/frequency-analysis?text=Wklv+lv+d+vhfuhw+phvvdjh+derxw+d+fdhvdu+flskhu+zlwk+d+ixqqb+vkliw' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Ftext-ciphers.x402tookit.com%2Ffrequency-analysis
const res = await pay("https://text-ciphers.x402tookit.com/frequency-analysis?text=Wklv+lv+d+vhfuhw+phvvdjh+derxw+d+fdhvdu+flskhu+zlwk+d+ixqqb+vkliw");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://text-ciphers.x402tookit.com/frequency-analysis?text=Wklv+lv+d+vhfuhw+phvvdjh+derxw+d+fdhvdu+flskhu+zlwk+d+ixqqb+vkliw")
    print(res.status_code, res.text)