Composable security against collective attacks of a modified BB84 QKD protocol with information only in one basis
This work addresses security for quantum key distribution protocols, but it is incremental as it builds on prior frameworks without major breakthroughs.
The paper analyzes the security of a modified BB84 QKD protocol that sends information only in the z basis while testing in both z and x bases, showing it is as secure as the original BB84 against collective attacks but requires more bits for testing.
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.