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 modular framework for constructing secure key leasing with a classical-lessor, where the lessor is entirely classical and, in particular, the quantum secret key can be both leased and revoked using only classical communication. Based on this framework, we obtain classical-lessor secure key leasing schemes for public-key encryption (PKE), pseudorandom function (PRF), and digital signature. We adopt the strong security notion known as security against verification key revealing attacks (VRA security) proposed by Kitagawa et al. (Eurocrypt 2025) into the classical-lessor setting, and we prove that all three of our schemes satisfy this notion under the learning with errors assumption. Our PKE scheme improves upon the previous construction by Goyal et al. (Eurocrypt 2025), and our PRF and digital signature schemes are respectively the first PRF and digital signature with classical-lessor secure key leasing property.

翻译：安全密钥租赁允许将密码学密钥以量子态的形式出租，使得该密钥随后能以可验证的方式被撤销。在本工作中，我们提出了一个模块化框架，用于构建具有经典出租方的安全密钥租赁方案，其中出租方完全是经典的，特别是量子密钥的租赁和撤销均可仅通过经典通信完成。基于此框架，我们获得了针对公钥加密、伪随机函数和数字签名的经典出租方安全密钥租赁方案。我们将Kitagawa等人（Eurocrypt 2025）提出的、被称为抗验证密钥泄露攻击安全性的强安全概念引入经典出租方场景，并证明在容错学习假设下，我们的三个方案均满足该安全概念。我们的公钥加密方案改进了Goyal等人（Eurocrypt 2025）先前的构造，而我们的伪随机函数和数字签名方案分别是首个具有经典出租方安全密钥租赁特性的伪随机函数和数字签名方案。