ITPEC FE Subject B October 2024 Question 18
ITPEC FE Subject B October 2024 — Question 18 of 20
Password Entropy — calculating password strength in bits using the entropy formula.
The formula for password entropy is:
E = ⌊L × log₂(R)⌋
where L = password length, R = size of the character pool, and ⌊⌋ = floor function.
Step-by-step:
- Identify character types in A6GmyVyOC: uppercase letters (
A, G, V, O, C), lowercase letters (m, y, y), digits (6) → three types used. - Calculate pool size:
R = 26 + 26 + 10 = 62. - Count length:
L = 9. - Apply the formula:
E = ⌊9 × log₂(62)⌋ = ⌊9 × 5.954⌋ = ⌊53.59⌋ = 53bits.
Why not others:
- (a) 42 — would result from using R = 26 (lowercase only), ignoring digits and uppercase
- (b) 51 — does not match any valid combination of R and L
- (c) 52 — would result from L = 8 with R = 94 (all character types); wrong length and wrong pool
- (e) 58 — would require a larger pool or longer password than given
Key rule: determine R by counting which character types are present (not which specific characters), then apply E = ⌊L × log₂(R)⌋.
AI-generated — may contain errors
The original exam layout is preserved in the image so diagrams, formulas, tables, and code remain accurate.
This question comes from an official ITPEC past paper. ITPEC Practice is an independent study tool and is not affiliated with ITPEC. See the official FE past-paper collection or Report an issue.