CISSP · Question #1464
An organization is implementing data encryption using symmetric ciphers and the Chief Information Officer (CIO) is concerned about the risk of using one key to protect all sensitive data, The…
The correct answer is B. Use a hierarchy of encryption keys. The CIO is concerned about the risk concentration of using a single symmetric key for all sensitive data. A key hierarchy mitigates this by using separate keys for different data sets, managed by a master key.
Question
An organization is implementing data encryption using symmetric ciphers and the Chief Information Officer (CIO) is concerned about the risk of using one key to protect all sensitive data, The security practitioner has been tasked with recommending a solution to address the CIO's concerns, Which of the following is the BEST approach to achieving the objective by encrypting all sensitive data?
Options
- AUse a Secure Hash Algorithm 256 (SHA-256).
- BUse a hierarchy of encryption keys.
- CUse Hash Message Authentication Code (HMAC) keys.
- DUse Rivest-Shamir-Adleman (RSA) keys.
How the community answered
(54 responses)- A7% (4)
- B78% (42)
- C4% (2)
- D11% (6)
Why each option
The CIO is concerned about the risk concentration of using a single symmetric key for all sensitive data. A key hierarchy mitigates this by using separate keys for different data sets, managed by a master key.
SHA-256 is a cryptographic hash function used for integrity verification, not data encryption, so it cannot encrypt sensitive data at all.
A hierarchy of encryption keys (e.g., master key encrypting data encryption keys, or DEKs) isolates risk so that compromise of one DEK only exposes the data it protects, not all sensitive data. This is a standard key management practice in symmetric encryption systems such as those defined by NIST SP 800-57, where Key Encryption Keys (KEKs) wrap individual DEKs, limiting the blast radius of any single key compromise.
HMAC is a message authentication mechanism used to verify data integrity and authenticity, not to encrypt data, and does not address the risk of a single encryption key.
RSA is an asymmetric (public-key) cipher, not a symmetric cipher, and while it can be used for key exchange, it does not directly solve the symmetric key hierarchy problem the CIO is concerned about.
Concept tested: Symmetric encryption key hierarchy and key management
Source: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r5.pdf
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