A healthcare organization wants to perform analytics on encrypted patient data without decrypting it first, to maintain privacy. Which cryptographic technique supports this use case?
Allows computation on encrypted data without decryption.
Why this answer
Homomorphic encryption allows computations to be performed directly on ciphertext, producing an encrypted result that, when decrypted, matches the result of operations performed on the plaintext. This enables the healthcare organization to run analytics on encrypted patient data without ever exposing the underlying sensitive information, thus preserving privacy throughout the processing lifecycle.
Exam trap
ISC2 often tests the distinction between 'processing on encrypted data' and 'protecting data at rest or in transit'—candidates mistakenly choose FPE or tokenization because they see 'encrypted' or 'token' and assume it supports analytics, but neither allows computation without decryption.
How to eliminate wrong answers
Option B (Tokenization) is wrong because it replaces sensitive data with non-sensitive tokens, but the original data must be stored in a separate vault and analytics cannot be performed on the tokens without detokenization, which breaks the 'no decryption' requirement. Option C (Format-preserving encryption) is wrong because it produces ciphertext that retains the original data format (e.g., 16-digit credit card numbers), but all operations require decryption first; it does not support computation on encrypted data. Option D (Cryptographic hashing) is wrong because it is a one-way function that cannot be reversed, and it does not allow any meaningful analytics on the hash values (e.g., you cannot compute an average or sum of hashed patient ages).