Glossary
Short, plain-language definitions for terms used elsewhere on this site. Each links back to the page where it’s explained in more depth.
Boolean circuit
A function written as a network of AND, OR, XOR, and NOT logic gates wired together — the same representation digital hardware uses. Garbled circuits work on a function once it’s been expressed this way; see what garbled circuits are.
Evaluator
The party in a garbled-circuit protocol who receives the garbled tables and a set of wire labels, and computes the circuit gate by gate to reach the output — without ever seeing a plaintext 0 or 1 for any wire in between. See what garbled circuits are for the Evaluator’s role, and how it works for exactly how a single gate gets evaluated.
Garbled table
The encrypted version of a single gate’s truth table — four ciphertexts (for a two-input gate), one per input combination, shuffled into random order so that position reveals nothing either. Built by the Garbler; consumed by the Evaluator. See how it works for the exact construction.
Garbler
The party in a garbled-circuit protocol who builds the circuit, generates wire labels, encrypts every gate into a garbled table, and hands the whole thing to the Evaluator. See what garbled circuits are.
Malicious security
A security model where a protocol must remain safe even if a corrupted party actively deviates from the protocol — lying about inputs, sending malformed messages, aborting early to leak information, and so on. Stronger (and generally more expensive) than semi-honest security. The construction on this site is analyzed only in the semi-honest model.
Oblivious Transfer (OT)
A cryptographic primitive where a sender offers two values and a receiver picks up exactly one of their choosing — the sender never learns which one was picked, and the receiver never sees the other one. In a real garbled-circuit protocol, OT is how the Evaluator obtains the correct wire label for each of their own private input bits, without revealing that bit to the Garbler. The demo on this site’s Interactive page skips OT — see how it works for exactly why that’s a legitimate simplification there but would be a critical security hole in a real two-party protocol.
Semi-honest security
A security model (also called “honest-but-curious”) where every party is assumed to follow the protocol exactly as specified, but may try to learn extra information from whatever messages they legitimately receive. Weaker than malicious security, but simpler to achieve and the standard starting point for understanding a protocol — including the one on this site.
Wire label
A random 128-bit value assigned to one possible value (0 or 1) of one wire in a circuit. Every wire gets two labels, one per bit value, and — critically — nothing about a label’s bit pattern reveals which value it represents. See how it works for exactly how labels are generated and used.
Sources: these are standard definitions used consistently across the secure-computation literature; see History for citations to the original papers that introduced several of these concepts.