Page 1 of 134
Intro to Cryptography Bundle with
complete solutions.
Q1. What is the primary goal of cryptography?
A) Data compression
B) Data confidentiality
C) Data deletion
D) Data duplication
Answer: B | Rationale: Cryptography's core goal is ensuring
confidentiality by converting plaintext into ciphertext, making it
unreadable to unauthorized parties. While it also supports
integrity and authentication, confidentiality is the primary
objective.
Q2. Which of the following best describes "plaintext"?
A) Encrypted data
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B) Readable, unencrypted data
C) A cryptographic key
D) A hashed message
Answer: B | Rationale: Plaintext is the original, human-
readable or machine-readable information before any
encryption process is applied.
Q3. In a Caesar cipher with a shift of 3, what is the ciphertext
for "HELLO"?
A) KHOOR
B) KHOOR
C) IFMMP
D) EBIIL
Answer: A (KHOOR) | Rationale: Each letter shifts forward by
3: H→K, E→H, L→O, L→O, O→R. This is a simple substitution
cipher vulnerable to frequency analysis.
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Q4. (Scenario) You find an ancient manuscript with the text
"WKH TXLFN EURZQ IRA MXPSV RYHU WKH ODCB GRJ." What
is the most likely decryption method?
A) ROT13
B) Atbash cipher
C) Caesar shift of 3
D) Vigenère cipher
Answer: C | Rationale: The phrase "WKH" (the) and "TXLFN"
(quick) suggest a Caesar shift of -3 (or +23). "WKH" shifts back
to "THE", confirming ROT3 encryption.
Q5. Which historical cipher uses a keyword to create multiple
Caesar shifts?
A) Playfair
B) Vigenère
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C) Rail Fence
D) Atbash
Answer: B | Rationale: The Vigenère cipher applies different
Caesar shifts based on a repeating keyword, making it more
resistant to simple frequency analysis than monoalphabetic
ciphers.
Q6. What is the key space size for a simple substitution cipher
(English alphabet, 26 letters)?
A) 26
B) 26!
C) 2^26
D) 26^2
Answer: B (26!) | Rationale: There are 26! (approximately
2^88) possible mappings, but linguistic patterns reduce the
effective security, making it breakable with frequency analysis.
Intro to Cryptography Bundle with
complete solutions.
Q1. What is the primary goal of cryptography?
A) Data compression
B) Data confidentiality
C) Data deletion
D) Data duplication
Answer: B | Rationale: Cryptography's core goal is ensuring
confidentiality by converting plaintext into ciphertext, making it
unreadable to unauthorized parties. While it also supports
integrity and authentication, confidentiality is the primary
objective.
Q2. Which of the following best describes "plaintext"?
A) Encrypted data
,Page 2 of 134
B) Readable, unencrypted data
C) A cryptographic key
D) A hashed message
Answer: B | Rationale: Plaintext is the original, human-
readable or machine-readable information before any
encryption process is applied.
Q3. In a Caesar cipher with a shift of 3, what is the ciphertext
for "HELLO"?
A) KHOOR
B) KHOOR
C) IFMMP
D) EBIIL
Answer: A (KHOOR) | Rationale: Each letter shifts forward by
3: H→K, E→H, L→O, L→O, O→R. This is a simple substitution
cipher vulnerable to frequency analysis.
,Page 3 of 134
Q4. (Scenario) You find an ancient manuscript with the text
"WKH TXLFN EURZQ IRA MXPSV RYHU WKH ODCB GRJ." What
is the most likely decryption method?
A) ROT13
B) Atbash cipher
C) Caesar shift of 3
D) Vigenère cipher
Answer: C | Rationale: The phrase "WKH" (the) and "TXLFN"
(quick) suggest a Caesar shift of -3 (or +23). "WKH" shifts back
to "THE", confirming ROT3 encryption.
Q5. Which historical cipher uses a keyword to create multiple
Caesar shifts?
A) Playfair
B) Vigenère
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C) Rail Fence
D) Atbash
Answer: B | Rationale: The Vigenère cipher applies different
Caesar shifts based on a repeating keyword, making it more
resistant to simple frequency analysis than monoalphabetic
ciphers.
Q6. What is the key space size for a simple substitution cipher
(English alphabet, 26 letters)?
A) 26
B) 26!
C) 2^26
D) 26^2
Answer: B (26!) | Rationale: There are 26! (approximately
2^88) possible mappings, but linguistic patterns reduce the
effective security, making it breakable with frequency analysis.
