Which process achieves group agreement without a centralized unit?

• A. Biometric Impersonation
• B. Secure Function Evaluation (SFE)
• C. Private Function Evaluation (PFE)
• D. Distributed Consensus

Answer: (D)

The main idea here is coordinating many participants to agree on a single value without relying on any central authority. Distributed consensus provides exactly that: protocols that let all non-faulty nodes decide on the same data item, even if some nodes fail or messages are delayed. It enforces safety (no two correct nodes decide differently) and often tries to ensure progress (liveness) despite faults. This capability is what underpins distributed databases and blockchain networks that operate without a central coordinator. The other terms refer to different ideas: secure function evaluation is about computing a function securely across parties, private function evaluation adds privacy to the inputs, and biometric impersonation is a security threat involving pretending to be someone else rather than achieving group agreement.