Quick Answer
The answer is loss of confidentiality. In CBC mode, the initialization vector is XORed with the first plaintext block before encryption, and reusing the same IV with the same key means that identical plaintext blocks will always produce identical ciphertext blocks, directly revealing data patterns and enabling an attacker to infer message structure or recover plaintext through known-plaintext attacks. On the Systems Security Certified Practitioner SSCP exam, this concept tests your understanding of cryptographic implementation flaws, often appearing in scenario-based questions where a security analyst reviews a misconfigured system; a common trap is confusing this with integrity loss, but the core risk is always about confidentiality, not data tampering. Remember the mnemonic: “IV reuse, patterns ooze”—if the IV repeats, so do the ciphertexts, breaking secrecy.
This SSCP practice question tests your understanding of cryptography. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A security analyst reviews a cryptographic implementation and notices that the same initialization vector (IV) is used repeatedly with the same key in CBC mode. What is the primary risk?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Loss of confidentiality
IV reuse can lead to identical ciphertext blocks for identical plaintext, revealing patterns.
Loss of authentication
Why wrong: IV reuse does not affect authentication.
Non-repudiation is compromised
Why wrong: Non-repudiation is unrelated to IV reuse.
Loss of integrity
Why wrong: IV reuse does not directly affect integrity.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Loss of confidentiality
In CBC (Cipher Block Chaining) mode, the initialization vector (IV) is XORed with the first plaintext block before encryption. Reusing the same IV with the same key means that identical plaintext blocks will produce identical ciphertext blocks, revealing patterns in the data. This directly breaks confidentiality, as an attacker can detect repeated plaintext segments, infer message structure, or even recover plaintext through known-plaintext attacks.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Loss of confidentiality
Why this is correct
IV reuse can lead to identical ciphertext blocks for identical plaintext, revealing patterns.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Loss of authentication
Why it's wrong here
IV reuse does not affect authentication.
Non-repudiation is compromised
Why it's wrong here
Non-repudiation is unrelated to IV reuse.
Loss of integrity
Why it's wrong here
IV reuse does not directly affect integrity.
Common exam traps
The trap here is that candidates often confuse confidentiality with integrity or authentication, mistakenly thinking IV reuse primarily enables data tampering (integrity) or impersonation (authentication), when in fact the core cryptographic weakness is the exposure of plaintext patterns, directly violating confidentiality.
Detailed technical explanation
CBC mode works by XORing each plaintext block with the previous ciphertext block (or the IV for the first block). If the IV is fixed, the first block of ciphertext becomes deterministic for a given key and plaintext, enabling frequency analysis and known-plaintext attacks. In real-world protocols like TLS 1.0, IV reuse was exploited in the BEAST attack, where an attacker could predict the IV and decrypt HTTPS cookies by observing repeated ciphertext blocks.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
What to study next
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FAQ
Cryptography — This question tests Cryptography — Read the scenario before looking for a memorised answer..
The correct answer is: Loss of confidentiality — In CBC (Cipher Block Chaining) mode, the initialization vector (IV) is XORed with the first plaintext block before encryption. Reusing the same IV with the same key means that identical plaintext blocks will produce identical ciphertext blocks, revealing patterns in the data. This directly breaks confidentiality, as an attacker can detect repeated plaintext segments, infer message structure, or even recover plaintext through known-plaintext attacks.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 25, 2026
This SSCP practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SSCP exam.
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