11 papers
Trapdoor Functions with Secure Key Leasing and Copy Protection
Fuyuki Kitagawa, Ryo Nishimaki, Yuki Shirakawa +1
Inspired by the no-cloning theorem in quantum theory, a variety of quantum cryptographic primitives with unclonable functionalities, such as secure key leasing and copy protection,…
Towards the Impossibility of Imperfectly Complete Key Agreement in the QROM
Fuyuki Kitagawa, Ryo Nishimaki, Agi Villanyi +1
We make progress towards the impossibility of imperfectly complete quantum-computation, classical-communication (QCCC) key agreement by constructing the first unconditional attacks…
Multi-Copy Security in Unclonable Cryptography
Alper Çakan, Vipul Goyal, Fuyuki Kitagawa +2
Unclonable cryptography leverages the quantum no-cloning principle to copy-protect cryptographic functionalities. While most existing works address the basic single-copy security,…
Collusion-Resistant Quantum Secure Key Leasing Beyond Decryption
Fuyuki Kitagawa, Ryo Nishimaki, Nikhil Pappu
Secure key leasing (SKL) enables the holder of a secret key for a cryptographic function to temporarily lease the key using quantum information. Later, the recipient can produce a…
A Unified Approach to Quantum Key Leasing with a Classical Lessor
Fuyuki Kitagawa, Jiahui Liu, Shota Yamada +1
Secure key leasing allows a cryptographic key to be leased as a quantum state in such a way that the key can later be revoked in a verifiable manner. In this work, we propose a mod…
PKE and ABE with Collusion-Resistant Secure Key Leasing
Fuyuki Kitagawa, Ryo Nishimaki, Nikhil Pappu
Secure key leasing (SKL) is an advanced encryption functionality that allows a secret key holder to generate a quantum decryption key and securely lease it to a user. Once the user…