Which concept permits performing computations on encrypted data?

• A. Homomorphic Encryption
• B. Private Information Retrieval (PIR)
• C. Blockchain
• D. Distributed Consensus

Answer: (A)

The ability to compute on encrypted data is provided by homomorphic encryption. This cryptographic approach lets you perform operations directly on ciphertexts, and when you decrypt the result, it matches the outcome you would get if you had performed the same operations on the plaintext. That means you can have data processed in an untrusted environment, like a cloud service, without ever exposing the underlying information. Some schemes support specific operations like addition or multiplication on encrypted data, while fully homomorphic encryption allows arbitrary computations, though it can be resource-intensive in practice. This capability is what makes it the right fit for the question.

Private Information Retrieval focuses on retrieving data without revealing which item is being retrieved, not on performing calculations on encrypted data. Blockchain and distributed consensus deal with how data is stored, shared, and agreed upon across a network, rather than enabling computations over encrypted content.