Weak coin flipping is a cryptographic primitive in which two mutually distrustful parties generate a shared random bit to agree on a winner via remote communication. While a stand-alone secure weak coin flipping protocol can be constructed from noiseless communication channels, its composability has not been explored. In this work, we demonstrate that no weak coin flipping protocol can be abstracted into a black box resource with composable security. Despite this, we also establish the overall stand-alone security of weak coin flipping protocols under sequential composition.

翻译：弱掷币协议是一种密码学原语，两个互不信任的参与方通过远程通信生成一个共享随机比特，以确定获胜者。虽然基于无噪声通信信道可以构建独立的弱掷币安全协议，但其可组合性尚未得到研究。本文证明了任何弱掷币协议都无法被抽象为具有可组合安全性的黑盒资源。尽管如此，我们同时确立了弱掷币协议在顺序组合下的整体独立安全性。