gchq/CyberChef · error · OperationError

Error: Radix argument must be between 2 and 36

Error message

Error: Radix argument must be between 2 and 36

What it means

Thrown by the Luhn Checksum operation when the 'Radix' argument (args[0]) is outside the inclusive range 2–36. JavaScript's parseInt only supports radix 2–36, and the Luhn mod-N algorithm needs at least base 2, so run() rejects any other value at LuhnChecksum.mjs:77 with an OperationError. This check runs before any input is processed.

Source

Thrown at src/core/operations/LuhnChecksum.mjs:77

            }

            even = !even;
            return acc + temp;
        }, 0) % radix; // Use radix as the modulus base
    }

    /**
     * @param {string} input
     * @param {Object[]} args
     * @returns {string}
     */
    run(input, args) {
        if (!input) return "";

        const radix = args[0];

        if (radix < 2 || radix > 36) {
            throw new OperationError("Error: Radix argument must be between 2 and 36");
        }

        if (radix % 2 !== 0) {
            throw new OperationError("Error: Radix argument must be divisible by 2");
        }

        const checkSum = this.checksum(input, radix).toString(radix);
        let checkDigit = this.checksum(input + "0", radix);
        checkDigit = checkDigit === 0 ? 0 : (radix - checkDigit);
        checkDigit = checkDigit.toString(radix);

        return `Checksum: ${checkSum}
Checkdigit: ${checkDigit}
Luhn Validated String: ${input + "" + checkDigit}`;
    }

}

View on GitHub (pinned to 4290ea7539)

Solutions

1. Set Radix to an even integer between 2 and 36 inclusive (10 for classic Luhn, 36 for full alphanumeric).
2. If loading a recipe, clamp/validate the radix field before running.
3. For bases above 36, use a different operation — Luhn Checksum cannot represent them.

Example fix

// before
luhn.run(input, [64]);   // out of range

// after
luhn.run(input, [36]);   // valid even radix within 2..36

function validLuhnRadix(r) {
  return Number.isInteger(r) && r >= 2 && r <= 36 && r % 2 === 0;
}
if (!validLuhnRadix(radix)) {
  throw new Error('Radix must be an even integer between 2 and 36');
}

function isLuhnRadix(v: unknown): v is number {
  return typeof v === 'number' && Number.isInteger(v) && v >= 2 && v <= 36 && v % 2 === 0;
}

When it happens

Trigger: Setting the Radix argument to a number less than 2 or greater than 36 — e.g. 0, 1, 37, 64, or a negative value. Triggered at LuhnChecksum.mjs:76-78 before checksum() is called.

Common situations: Default value edited to an out-of-range number; a recipe JSON carrying a stale/invalid radix; confusing the radix with a modulo or checksum length; passing a base-64 expectation (not supported — max is 36).

Related errors

• Character: ${elem} is not valid in radix ${radix}.
• Error: Radix argument must be divisible by 2
• Invalid custom CRC arguments
• Unknown checksum algorithm
• Size must be between 0 and 512

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/df87d42ca306a6c3. Report an issue: GitHub.