Quantum information processing is reshaping both the theory and practice of computer science, with cryptography undergoing this transformation particularly intensely. The interface between quantum computation and cryptography spans a broad and fascinating spectrum of questions. At one end are practical challenges: designing classical protocols that run on a laptop, yet remain secure against adversaries equipped with large-scale quantum computers. On the theoretical side are questions about pseudorandom quantum states serving as a possibly minimal assumption for cryptography, as well as the development of generalized proof systems in which witnesses may be quantum states rather than classical strings. At the other end of this spectrum lies a vision of the future of communication, asking what forms of cryptography are possible when quantum computers are available not only to adversaries, but also to honest parties.
In this talk, I will survey this interface with a focus on my research. I will then present a new cryptographic primitive from my work, called one-shot signatures, which enables new capabilities across several domains: it overcomes key impossibilities in decentralized systems, and allows the realization of quantum cryptographic tasks using only classical communication and local quantum computation.
