We consider an enhanced measure of security for a quantum key distribution protocol, in which we require that the adversary not only obtains no information about the key but also remains unaware that a key generation protocol has been executed. When the adversary applies the same quantum channel independently to each transmitted quantum state, akin to a collective attack in the quantum key distribution literature, we propose a protocol that achieves covert and secret key expansion under mild restrictions. A crucial component of the protocol is a covert estimation stage, which is then combined with universal channel coding for reliability and resolvability in the covert regime.

中文翻译：

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集体攻击下量子信道上的秘密密钥扩展

我们考虑增强量子密钥分发协议的安全性，其中我们要求对手不仅无法获得有关密钥的信息，而且仍然不知道已执行密钥生成协议。当对手独立地将相同的量子通道应用于每个传输的量子状态时，类似于量子密钥分发文献中的集体攻击，我们提出了一种协议，在温和的限制下实现秘密密钥扩展。该协议的一个关键组成部分是隐蔽估计阶段，然后将其与通用信道编码相结合，以实现隐蔽机制中的可靠性和可解析性。