Which term refers to computing on encrypted data without decrypting it?

• A. Blockchain
• B. Passwordless Authentication
• C. Homomorphic Encryption
• D. Private Information Retrieval (PIR)

Answer: (C)

Computing on encrypted data without decrypting it is achieved with homomorphic encryption. This cryptographic approach lets operations be performed directly on ciphertexts, and when you decrypt the result, it matches the outcome you would have gotten if you’d performed the same operations on the plaintext. That means you can outsource processing to an external party, like a cloud service, while keeping the actual data hidden the whole time.

Fully homomorphic encryption supports any computation on encrypted data, while partial or somewhat homomorphic schemes support a limited set of operations. This concept is what enables privacy-preserving analytics, secure cloud computing, and other applications where data confidentiality is crucial even during processing.

Other terms mentioned don’t fit this idea. Blockchain is a distributed ledger technology, passwordless authentication focuses on how you verify identity without passwords, and Private Information Retrieval lets you fetch data without revealing which item you’re retrieving but doesn’t enable performing computations on encrypted data.