📝 One time passwords

📖 From Operating System • 15. Security • 12 questions available

Practice MCQs for One time passwords. Test your knowledge with carefully crafted questions across easy, medium, and hard difficulty levels.

🔄 Last updated: 2026-07-27

Easy Questions

Medium Questions

Hard Questions

Q1. What best describes a one-time password (OTP)?

🔹 A. A password that never expires

🔹 B. A password that is valid for only a single authentication session

🔹 C. A password that is shared among multiple users

🔹 D. A password stored in plaintext on the server

💡 Difficulty: easy | ✅ Correct: B

Q2. In a Time‑Based OTP (TOTP) system, how is the current password generated?

🔹 A. By hashing a secret key with the current Unix timestamp divided by a time step

🔹 B. By incrementing a counter each time a password is requested

🔹 C. By encrypting the user’s static password with a random nonce

🔹 D. By storing pre‑computed passwords on the server

💡 Difficulty: medium | ✅ Correct: A

Q3. If an attacker obtains the shared secret used for TOTP generation, what is the impact on the system’s security?

🔹 A. The attacker can generate valid OTPs for any time interval

🔹 B. The attacker can only guess OTPs with a 50% success rate

🔹 C. The attacker can replay previously captured OTPs indefinitely

🔹 D. The attacker’s knowledge has no effect without the user’s device

💡 Difficulty: hard | ✅ Correct: A

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