gchq/CyberChef · error · OperationError

Crib cannot be empty

Error message

Crib cannot be empty

What it means

The Bombe attack requires a known-plaintext 'crib' to test against ciphertext. If the crib argument is empty after extraction, the operation cannot form any hypothesis and throws immediately, before rotor setup.

Source

Thrown at src/core/operations/Bombe.mjs:135

        const offset = args[7];
        const check = args[8];
        const rotors = [];
        for (let i=0; i<4; i++) {
            if (i === 0 && model === "3-rotor") {
                // No fourth rotor
                continue;
            }
            let rstr = args[i + 1];
            // The Bombe doesn't take stepping into account so we'll just ignore it here
            if (rstr.includes("<")) {
                rstr = rstr.split("<", 2)[0];
            }
            rotors.push(rstr);
        }
        // Rotors are handled in reverse
        rotors.reverse();
        if (crib.length === 0) {
            throw new OperationError("Crib cannot be empty");
        }
        if (offset < 0) {
            throw new OperationError("Offset cannot be negative");
        }
        // For symmetry with the Enigma op, for the input we'll just remove all invalid characters
        input = input.replace(/[^A-Za-z]/g, "").toUpperCase();
        crib = crib.replace(/[^A-Za-z]/g, "").toUpperCase();
        const ciphertext = input.slice(offset);
        const reflector = new Reflector(reflectorstr);
        let update;
        if (isWorkerEnvironment()) {
            update = this.updateStatus;
        } else {
            update = undefined;
        }
        const bombe = new BombeMachine(rotors, reflector, ciphertext, crib, check, update);
        const result = bombe.run();
        return {

View on GitHub (pinned to 4290ea7539)

Solutions

1. Supply a non-empty crib (the suspected plaintext fragment) as an argument.
2. Validate crib.length > 0 in the UI before allowing the recipe to run.
3. Confirm the argument order matches the operation's ingList.

Example fix

// before
crib = ''
// after
crib = 'WETTER'

if (!crib || crib.length === 0) throw new Error('Crib is required for the Bombe');

function hasCrib(c) { return typeof c === 'string' && c.length > 0; }

When it happens

Trigger: Calling Bombe.run with an empty crib argument string (length 0 before any character filtering).

Common situations: User leaves the crib field blank; UI default empty string; the crib variable was not bound from the recipe.

Related errors

• Offset cannot be negative
• Invalid ciphertext length: ${originalLength} bytes. Must be
• No padding requested in ${mode} mode but input is not a 16-b
• With ECB or CBC modes, the input must be divisible into 16 b
• No padding requested but input length (${message.length} byt

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/5a3b2dcb8bcf057a. Report an issue: GitHub.