Quick Answer
The answer is AES, along with RSA and 3DES, as these three are the most commonly used encryption standards in modern IT security. AES, or Advanced Encryption Standard, is a symmetric-key block cipher that encrypts data in fixed 128-bit blocks using key sizes of 128, 192, or 256 bits, making it both fast and highly secure for bulk data encryption. RSA, an asymmetric algorithm, relies on the mathematical difficulty of factoring large prime numbers to secure key exchange and digital signatures, while 3DES applies the older DES algorithm three times to each block, effectively increasing key length to 168 bits—though it is now considered legacy due to slower performance and weaker security compared to AES. On the CISA exam, this question tests your understanding of foundational encryption standards used in data protection controls; a common trap is confusing DES with 3DES or overlooking that RSA is asymmetric while AES and 3DES are symmetric. Remember the mnemonic “A3R” to recall AES, 3DES, and RSA as the trio of commonly used encryption standards.
This CISA practice question tests your understanding of protection of information assets. 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.
Which THREE of the following are commonly used data encryption standards? (Choose three.)
3DES
Triple DES, symmetric encryption.
SHA-256
Why wrong: SHA-256 is a secure hash algorithm, not encryption.
RSA
Rivest-Shamir-Adleman, asymmetric encryption.
AES
Advanced Encryption Standard, symmetric encryption.
MD5
Why wrong: MD5 is a hash function, not encryption.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
3DES
3DES (Triple Data Encryption Standard) is a symmetric-key block cipher that applies the DES algorithm three times to each data block, effectively increasing the key length to 168 bits. It was widely adopted as a secure replacement for single DES, though it is now considered legacy due to performance and security limitations.
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.
3DES
Why this is correct
Triple DES, symmetric encryption.
Related concept
Read the scenario before looking for a memorised answer.
SHA-256
Why it's wrong here
SHA-256 is a secure hash algorithm, not encryption.
RSA
Why this is correct
Rivest-Shamir-Adleman, asymmetric encryption.
Related concept
Read the scenario before looking for a memorised answer.
AES
Why this is correct
Advanced Encryption Standard, symmetric encryption.
Related concept
Read the scenario before looking for a memorised answer.
MD5
Why it's wrong here
MD5 is a hash function, not encryption.
Common exam traps
The trap here is confusing cryptographic hash functions (SHA-256, MD5) with encryption standards, leading candidates to select them as methods for protecting data confidentiality rather than integrity.
Detailed technical explanation
Encryption standards like 3DES, AES, and RSA are designed for data confidentiality, whereas hash functions like SHA-256 and MD5 are one-way functions used for integrity verification. AES, the current NIST-approved symmetric standard, uses block sizes of 128 bits and key sizes of 128, 192, or 256 bits, offering significantly better performance and security than 3DES. RSA is an asymmetric algorithm relying on the difficulty of factoring large prime numbers, commonly used for key exchange and digital signatures.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the CISA exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Protection of Information Assets — This question tests Protection of Information Assets — Read the scenario before looking for a memorised answer..
The correct answer is: 3DES — 3DES (Triple Data Encryption Standard) is a symmetric-key block cipher that applies the DES algorithm three times to each data block, effectively increasing the key length to 168 bits. It was widely adopted as a secure replacement for single DES, though it is now considered legacy due to performance and security limitations.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This CISA practice question is part of Courseiva's free ISACA 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 CISA exam.
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