Composable security against collective attacks of a modified BB84 QKD protocol with information only in one basis

Abstract

Quantum Cryptography uses the counter-intuitive properties of Quantum Mechanics for performing cryptographic tasks in a secure and reliable way. The Quantum Key Distribution (QKD) protocol BB84 has been proven secure against several important types of attacks: collective attacks and joint attacks. Here we analyze the security of a modified BB84 protocol, for which information is sent only in the z basis while testing is done in both the z and the x bases, against collective attacks. The proof follows the framework of a previous paper (Boyer, Gelles, and Mor, 2009), but it avoids a classical information-theoretical analysis and proves a fully composable security. We show that this modified BB84 protocol is as secure against collective attacks as the original BB84 protocol, and that it requires more bits for testing.

24 pages; 1 figure; this is an improved version of arXiv:1704.01388 [quant-ph], extended to make the security proof (against collective attacks) fully composable

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• Security Against Collective Attacks of a Modified BB84 QKD Protocol with Information only in One Basis