On the composable security of weak coin flipping

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.

@article{wu2025_2402.15233,
  title={ On the composable security of weak coin flipping },
  author={ Jiawei Wu and Yanglin Hu and Akshay Bansal and Marco Tomamichel },
  journal={arXiv preprint arXiv:2402.15233},
  year={ 2025 }
}