gchq/CyberChef · error · OperationError

Ψ4 custom lugs must be 53 long and can only include . or x

Error message

Ψ4 custom lugs must be 53 long and can only include . or x

What it means

Thrown by the Lorenz operation only when 'Wheel Pattern' is 'Custom'. The Ψ4 wheel has 53 cams, so its lug pattern must be exactly 53 characters matching ^[.xX]*$. Guard is on line 285 of src/core/operations/Lorenz.mjs.

Source

Thrown at src/core/operations/Lorenz.mjs:285

        if (s3<1 || s3>51) throw new OperationError("Ψ3 start must be between 1 and 51");
        if (s4<1 || s4>53) throw new OperationError("Ψ4 start must be between 1 and 53");
        if (s5<1 || s5>59) throw new OperationError("Ψ5 start must be between 1 and 59");
        if (m37<1 || m37>37) throw new OperationError("Μ37 start must be between 1 and 37");
        if (m61<1 || m61>61) throw new OperationError("Μ61 start must be between 1 and 61");
        if (x1<1 || x1>41) throw new OperationError("Χ1 start must be between 1 and 41");
        if (x2<1 || x2>31) throw new OperationError("Χ2 start must be between 1 and 31");
        if (x3<1 || x3>29) throw new OperationError("Χ3 start must be between 1 and 29");
        if (x4<1 || x4>26) throw new OperationError("Χ4 start must be between 1 and 26");
        if (x5<1 || x5>23) throw new OperationError("Χ5 start must be between 1 and 23");

        // Initialise chosen wheel pattern
        let chosenSetting = "";
        if (pattern === "Custom") {
            const re = new RegExp("^[.xX]*$");
            if (lugs1.length !== 43 || !re.test(lugs1)) throw new OperationError("Ψ1 custom lugs must be 43 long and can only include . or x ");
            if (lugs2.length !== 47 || !re.test(lugs2)) throw new OperationError("Ψ2 custom lugs must be 47 long and can only include . or x");
            if (lugs3.length !== 51 || !re.test(lugs3)) throw new OperationError("Ψ3 custom lugs must be 51 long and can only include . or x");
            if (lugs4.length !== 53 || !re.test(lugs4)) throw new OperationError("Ψ4 custom lugs must be 53 long and can only include . or x");
            if (lugs5.length !== 59 || !re.test(lugs5)) throw new OperationError("Ψ5 custom lugs must be 59 long and can only include . or x");
            if (lugm37.length !== 37 || !re.test(lugm37)) throw new OperationError("M37 custom lugs must be 37 long and can only include . or x");
            if (lugm61.length !== 61 || !re.test(lugm61)) throw new OperationError("M61 custom lugs must be 61 long and can only include . or x");
            if (lugx1.length !== 41 || !re.test(lugx1)) throw new OperationError("Χ1 custom lugs must be 41 long and can only include . or x");
            if (lugx2.length !== 31 || !re.test(lugx2)) throw new OperationError("Χ2 custom lugs must be 31 long and can only include . or x");
            if (lugx3.length !== 29 || !re.test(lugx3)) throw new OperationError("Χ3 custom lugs must be 29 long and can only include . or x");
            if (lugx4.length !== 26 || !re.test(lugx4)) throw new OperationError("Χ4 custom lugs must be 26 long and can only include . or x");
            if (lugx5.length !== 23 || !re.test(lugx5)) throw new OperationError("Χ5 custom lugs must be 23 long and can only include . or x");
            chosenSetting = INIT_PATTERNS["No Pattern"];
            chosenSetting.S[1] = this.readLugs(lugs1);
            chosenSetting.S[2] = this.readLugs(lugs2);
            chosenSetting.S[3] = this.readLugs(lugs3);
            chosenSetting.S[4] = this.readLugs(lugs4);
            chosenSetting.S[5] = this.readLugs(lugs5);
            chosenSetting.M[1] = this.readLugs(lugm61);
            chosenSetting.M[2] = this.readLugs(lugm37);
            chosenSetting.X[1] = this.readLugs(lugx1);
            chosenSetting.X[2] = this.readLugs(lugx2);

View on GitHub (pinned to 4290ea7539)

Solutions

Provide a Ψ4 lugs string of exactly 53 characters using only '.', 'x', 'X'.
Edit a known-good 53-character pattern in place.
Pre-validate with /^[.xX]{53}$/ before running.

Example fix

// before: args[22] = "...x" (4 chars) -> throws
// after:  args[22] = ".xx...xxxxx.x.x.xx...x.xx.x.x..x.x.xx.x..x.x.x.x.x.x."  (53 chars) -> ok

Defensive patterns

Strategy: validation

Validate before calling

// Ψ4 lugs (args[22]) must match /^[.xX]{53}$/ when pattern === 'Custom'.
function validateCustomLugs(str, size, name) {
  if (typeof str !== "string" || !new RegExp(`^[.xX]{${size}}$`).test(str)) {
    throw new Error(`${name} lugs must be exactly ${size} chars of '.', 'x', or 'X'`);
  }
}
if (args[1] === "Custom") validateCustomLugs(args[22], 53, "Ψ4");

Type guard

const isPsi4Lugs = (s) => typeof s === "string" && /^[.xX]{53}$/.test(s);

Try / catch

try {
  lorenz.run(input, args);
} catch (err) {
  if (err instanceof OperationError && /Ψ4 custom lugs/.test(err.message)) {
    args[22] = ".xx...xxxxx.x.x.xx...x.xx.x.x..x.x.xx.x..x.x.x.x.x.x."; // known-good 53-char pattern
  } else throw err;
}

Prevention

Ψ4 lug strings must be exactly 53 characters (the longest psi wheel along with Ψ5's 59).
Edit in place; watch for accidental truncation.
Validate with /^[.xX]{53}$/ before running.

When it happens

Trigger: Calling Lorenz.run() with pattern='Custom' where args[22] (Ψ4 lugs) is not exactly 53 characters or contains characters other than '.', 'x', 'X'.

Common situations: Custom pattern with a Ψ4 string of the wrong length; a stray character or whitespace added during edit; pattern copied from Ψ3 (51) or Ψ5 (59).

Related errors

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/c7110fdd7ff48d29. Report an issue: GitHub.