2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/90925We prove that in the BB84 quantum cryptography protocol Alice and Bob do not need to make random bases-choice for each qubit: they can keep the same bases for entire blocks of qubits. It suffices that the raw key consists of many such qubit-blocks. The practical advantage of reducing the need for random number is emphasized.2 pages, 1 figureQuantum Physicstext