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Difficulty: MediumCIA Triad and Non-Repudiation

During a post-incident review at a logistics company, security analysts discovered that an administrator modified system event logs and disputed making any changes. The logging infrastructure maintained file integrity using standalone SHA-256 hashes stored alongside the logs, but because multiple staff members had write permissions to update those hash files, individual accountability could not be established. Which of the following solutions should the organization implement to achieve non-repudiation for log updates?

  1. Asymmetric digital signatures generated using individual private keysAnswer
  2. B
    Cryptographic hash generation using SHA-256 for each log batch
  3. C
    Symmetric bulk encryption using AES-256 with a shared secret key
  4. D
    Role-Based Access Control restricting log file permissions to read-only

Answer

Asymmetric digital signatures generated using individual private keys
Digital signatures enforce non-repudiation by combining a cryptographic hash with asymmetric key pairs. Because the private key is strictly held by a single individual, any signature verified using that individual's public key conclusively proves origin and authenticity, preventing the sender from denying their action.

Step-by-Step Solution

1
Analyze the problem requirement
The organization requires proof of origin for log entries so administrators cannot deny performing modifications.
Simple hashes prove integrity (data has not changed unintentionally), but do not prove identity (who generated or modified the data).
2
Evaluate cryptographic security services
Non-repudiation requires a mechanism tied uniquely to a single entity that cannot be forged by others sharing access.
Asymmetric cryptography pairs a private key (held exclusively by one user) with a public key (used by anyone to verify signatures).
3
Select the appropriate control
Digital signatures provide non-repudiation, integrity, and authentication simultaneously.
Because only the private key owner could have produced the signature, the signer cannot claim the log entry came from someone else.

Key Concept

Non-Repudiation vs. Integrity in the CIA Triad
Estimated Time:1m 0s
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Topics

CIA Triad and Non-Repudiation

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