2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/168552We report on a complete free-space field implementation of a modified Ekert91 protocol for quantum key distribution using entangled photon pairs. For each photon pair we perform a random choice between key generation and a Bell inequality. The amount of violation is used to determine the possible knowledge of an eavesdropper to ensure security of the distributed final key.5 pages ReVTeX, 3 figures; version v2 with updated references and minor corrections, author spelling fixedQuantum Physicstext