Practical Cryptography from Noisy Photonic Storage

We show how to implement secure oblivious transfer (OT) based on the realistic assumption that quantum storage of photonic qubits is noisy. We thereby consider collective storage attacks, i.e., the dishonest party attempts to store each incoming qubit separately. Our model is similar to the model of bounded-quantum storage, however, we consider an explicit noise model inspired by present day technology. If the honest parties can perform perfect quantum operations, then we show that the protocol is secure for any amount of noise. In case the honest participants are only able to perform noisy operations themselves, we analyze a practical protocol that can be implemented with qubits encoded in the polarization or phase of weak laser pulses. We show how to derive explicit tradeoffs between the amount of storage noise, the amount of noise in the operations performed by the honest participants and the security of the protocol. Our analysis easily carries over to quantum protocols for secure identification.