= Gilles Brassard
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<Gilles Brassard> is a <computer scientist> whose work with <Charles H. Bennett> established an influential approach to <quantum key distribution>. Their 1984 protocol, now called <BB84>, encodes information in <pure states> represented by <nonorthogonal vectors> and uses classical communication to compare the preparation and measurement choices.<Quantum cryptography: Public key distribution and coin tossing by Charles H. Bennett and Gilles Brassard>[Introduction and key-distribution protocol]{ref}
The physical idea is that an observer who does not know the preparation basis cannot extract the encoded information without risking detectable disturbance. The protocol therefore uses sampled outcomes to assess the shared data. Its classical discussion must be authenticated: otherwise an active intermediary could impersonate each participant. This connects the physics of <quantum measurement> with assumptions about the surrounding <cryptographic protocol>.<Quantum cryptography: Public key distribution and coin tossing by Charles H. Bennett and Gilles Brassard>[Introduction, passive versus active eavesdropping; protocol discussion]{ref}
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{title=Portrait of <Gilles Brassard>}
{description=Lëa-Kim Châteauneuf. https://creativecommons.org/licenses/by-sa/4.0/[CC BY-SA 4.0], via Wikimedia Commons.}
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