CISSP Practice Question: A security architect is designing a cryptographic…

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  Use symmetric encryption (e.g., AES-256) for all data and share keys out-of-band.

  Why it's wrong here

  Sharing symmetric keys out-of-band, such as via a physical meeting or a pre-agreed secure channel, becomes highly impractical and insecure as the number of communicating parties increases. Establishing a secure, trusted channel for each key exchange is a significant logistical challenge, making it prone to interception or compromise during transit. This method lacks scalability and robust key management, failing to meet the demands of a modern cryptographic system where dynamic key distribution is essential.

• ✗

  Use only asymmetric encryption (e.g., RSA) for all data.

  Why it's wrong here

  Using only asymmetric encryption for all data is computationally inefficient due to the complex mathematical operations involved in public-key cryptography. Encrypting large volumes of data with algorithms like RSA would introduce significant latency and consume excessive processing power, making the system prohibitively slow for practical applications. Asymmetric encryption is primarily designed for secure key exchange and digital signatures, not for bulk data confidentiality.

• ✓

  Use asymmetric encryption for key exchange and symmetric encryption for data (hybrid cryptosystem).

  Why this is correct

  A hybrid cryptosystem is the industry standard because it leverages the strengths of both symmetric and asymmetric encryption while mitigating their individual weaknesses. Asymmetric encryption, such as RSA or ECC, is used to securely exchange a temporary symmetric 'session key,' which is then used by symmetric algorithms like AES-256 for efficient bulk data encryption. This approach ensures secure key establishment without the performance overhead of asymmetric encryption for the actual data transfer, providing both confidentiality and efficiency.

• ✗

  Use hash functions (e.g., SHA-256) to ensure confidentiality.

  Why it's wrong here

  Hash functions, like SHA-256, are one-way mathematical functions designed to produce a fixed-size output (hash value) from an input, primarily used to ensure data integrity and authenticity. They do not provide confidentiality because the original data cannot be recovered from its hash value, nor do they obscure the content itself. While crucial for detecting tampering and verifying data consistency, hashing does not encrypt or hide the information, thus failing to protect its secrecy.

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