{"record":{"id":"309bbe7bf29d081a","repo":"gchq/CyberChef","slug":"3-start-must-be-between-1-and-29","errorCode":null,"errorMessage":"Χ3 start must be between 1 and 29","messagePattern":"Χ3 start must be between 1 and 29","errorType":"exception","errorClass":"OperationError","httpStatus":null,"severity":"error","filePath":"src/core/operations/Colossus.mjs","lineNumber":442,"sourceCode":"            throw new OperationError(\"Set Total must be between 0000 and 9999\");\n\n        // null|fast|slow for each of S1-5,M1-2,X1-5\n        const control = {\n            fast: args[43],\n            slow: args[44]\n        };\n\n        // Start positions\n        if (args[52]<1 || args[52]>43) throw new OperationError(\"Ψ1 start must be between 1 and 43\");\n        if (args[53]<1 || args[53]>47) throw new OperationError(\"Ψ2 start must be between 1 and 47\");\n        if (args[54]<1 || args[54]>51) throw new OperationError(\"Ψ3 start must be between 1 and 51\");\n        if (args[55]<1 || args[55]>53) throw new OperationError(\"Ψ4 start must be between 1 and 53\");\n        if (args[56]<1 || args[57]>59) throw new OperationError(\"Ψ5 start must be between 1 and 59\");\n        if (args[51]<1 || args[51]>37) throw new OperationError(\"Μ37 start must be between 1 and 37\");\n        if (args[50]<1 || args[50]>61) throw new OperationError(\"Μ61 start must be between 1 and 61\");\n        if (args[45]<1 || args[45]>41) throw new OperationError(\"Χ1 start must be between 1 and 41\");\n        if (args[46]<1 || args[46]>31) throw new OperationError(\"Χ2 start must be between 1 and 31\");\n        if (args[47]<1 || args[47]>29) throw new OperationError(\"Χ3 start must be between 1 and 29\");\n        if (args[48]<1 || args[48]>26) throw new OperationError(\"Χ4 start must be between 1 and 26\");\n        if (args[49]<1 || args[49]>23) throw new OperationError(\"Χ5 start must be between 1 and 23\");\n\n        const starts = {\n            X1: args[45], X2: args[46], X3: args[47], X4: args[48], X5: args[49],\n            M61: args[50], M37: args[51],\n            S1: args[52], S2: args[53], S3: args[54], S4: args[55], S5: args[56]\n        };\n\n        const colossus = new ColossusComputer(input, pattern, qbusin, qbusswitches, control, starts, settotal, limit);\n        const result = colossus.run();\n\n        return result;\n    }\n\n    /**\n     * Select Program\n     *","sourceCodeStart":424,"sourceCodeEnd":460,"githubUrl":"https://github.com/gchq/CyberChef/blob/4290ea753912378913b1f3f54e0fc5720afeda5d/src/core/operations/Colossus.mjs#L424-L460","documentation":"Colossus simulates the Lorenz SZ cipher; the chi-3 (Χ3) wheel has exactly 29 cam positions. The start position is a 1-based index, enforced by `if (args[47]<1 || args[47]>29)`. Any value outside [1, 29] is rejected before the simulation runs.","triggerScenarios":"Setting the 'Χ3 start' argument (args[47]) to 0, a negative number, or an integer greater than 29. Also when a transcribed key setting uses the wrong wheel length for chi-3.","commonSituations":"Off-by-one (0-based assumption); mistaking Χ3's length (29) for another wheel's; bulk-pasting a start vector where columns are misaligned.","solutions":["Set the Χ3 start argument to an integer in the inclusive range [1, 29].","Verify the value against the Lorenz SZ chi-3 wheel length of 29.","Validate all start positions programmatically against their per-wheel maximums before baking."],"exampleFix":"// before\nargs[47] = 30; // throws: Χ3 start must be between 1 and 29\n// after\nargs[47] = 29; // valid: chi-3 wheel has 29 positions","handlingStrategy":"validation","validationCode":"const CHI3_START_MAX = 29;\nfunction validChi3Start(v) {\n  return Number.isInteger(v) && v >= 1 && v <= CHI3_START_MAX;\n}\nif (!validChi3Start(starts.X3)) {\n  throw new Error(`Χ3 start ${starts.X3} out of range [1, ${CHI3_START_MAX}]`);\n}","typeGuard":"function isChi3Start(v) {\n  return Number.isInteger(v) && v >= 1 && v <= 29;\n}","tryCatchPattern":null,"preventionTips":["Validate each wheel start against its fixed size before baking.","Start positions are 1-based.","Keep a per-wheel size lookup table next to your start vector to catch transpositions."],"tags":["cyberchef","colossus","lorenz","range-check","validation","operation-error"],"backgroundTag":null,"analyzedSha":"4290ea753912378913b1f3f54e0fc5720afeda5d","analyzedAt":"2026-08-13T06:05:50.210Z","schemaVersion":2},"datasetVersion":"2026-08-13T09:17:06.757Z"}