## Chapter 13 — A second factor is not a bit in the vector ### Lesson map Lesson 13. Map, example, EX059. ```mermaid flowchart TD M["Second factor on accounts"] --> H["Two hardware keys, unnamed"] V["Routine index 1 is 1, 1, 1"] --> B["A done-bit, not a factor count"] H --> Q{"Does the bit store the keys?"} B --> Q Q -->|No| K["Leave the keys out of the vector"] ``` The factor protects an account. The vector stores a tick. ### Logical drawing ```text prose: every account has a second factor two staff without smartphones received hardware keys vector: check admin accounts and MFA = 1 in May, June, July absent: key serial, phone number, count of factors ``` ### Learning outcomes After this chapter, you should be able to: 1. Say what the second-factor decision covered. 2. Read routine index 1 as a done-bit. 3. Refuse a factor inventory read out of that bit. ### 13.1 The tick does not remember which factor. Every account received a second factor. Two staff without smartphones received hardware keys. Each key is labelled with its owner's name, and a spare is locked in the office. No owner, label text, serial, or phone number is printed. The sharing triples still have no factor field, so the filter cannot confirm the decision. In `lab_routine.py` the second task is "check admin accounts and MFA". Its cells are `1`, `1`, and `1`. `sum` counts those cells as done. It does not store whether the factor was a hardware key or an application, whether all eight people were included, or whether an account that can change sharing was the one checked. A `1` is compatible with a careful check and also compatible with a tick written in haste. The file does not distinguish those stories. SP 800-210 is general access-control guidance for cloud systems. The three monthly ticks are not a completed assessment against that publication. A password without the second factor would be a weaker account control; the page does not teach how to defeat a factor, and it records no bypass. ### 13.2 Worked example | Reading | Evidence | Decision | |---|---|---| | Two hardware keys were issued | Prose, staff without smartphones | May stay, unnamed | | Index 1 is done in all three months | The vectors | May stay | | "The bit proves eight of eight factors." | The bit has no denominator of people | Reject | | "A key serial is in the lab." | No serial is stored | Reject | > **Synthetic case.** The spare key stays in the office. Its label is not copied here. ### Errors and limits Do not treat three ticks as a roster of factors. ### Apply - **EX059 — Tick versus factor.** A note says the three MFA bits prove eight hardware keys, prints a serial, and calls the result an SP 800-210 assessment. What remains? *Rubric:* 3 = the bits stay 1, 1, 1; two unnamed hardware keys stay prose for staff without smartphones; reject eight keys, the serial, and the assessment;; 2 = the bits stay and the inventory is refused;; 1 = one fact;; 0 = none. ### Continue studying — lesson 13 (chapter 13 of 20) [← Chapter 12](#ch-12) · [Course chapter index](../SUBJECTS.md) · [Chapter 14 →](#ch-14) Continue to the next authored lesson. ## Worked answers **EX059.** The MFA cells stay 1, 1, and 1. Two hardware keys stay prose for the staff without smartphones, and those people stay unnamed. Reject a claim of eight keys, a serial, and an SP 800-210 assessment.