Unconditional Security Against Memory-Bounded Adversaries

Christian Cachin, Ueli M. Maurer

Andrej Bogdanov, Yuval Ishai, Akshayaram Srinivasan

Ivan Damgård, Serge Fehr, Louis Salvail +1 more

We initiate the study of two-party cryptographic primitives \nwith unconditional security, assuming that the adversary’s \nquantum memory is of bounded size. We show that oblivious \ntransfer and bit commitment can be implemented in this \nmodel using protocols where honest parties need no quantum \nmemory, whereas an adversarial player needs quantum \nmemory of size at least n/2 in order to break the protocol, \nwhere n is the number of qubits transmitted. This is \nin sharp contrast to the classical bounded-memory model, \nwhere we can only tolerate adversaries with memory of size \nquadratic in honest players’ memory size. Our protocols \nare efficient, non-interactive and can be implemented using \ntoday’s technology. On the technical side, a new entropic \nuncertainty relation involving min-entropy is established.

Ivan Damgård, Jesper Buus Nielsen, Rafail Ostrovsky +1 more

Ivan Damgård, Serge Fehr, Louis Salvail +1 more

We initiate the study of two-party cryptographic primitives with unconditional security, assuming that the adversary's quantum memory is of bounded size. We show that oblivious transfer and bit commitment can be implemented in this model using protocols where honest parties need no quantum memory, whereas an adversarial player needs quantum memory of size at least n/2 in order to break the protocol, where n is the number of qubits transmitted. This is in sharp contrast to the classical bounded-memory model, where we can only tolerate adversaries with memory of size quadratic in honest players' memory size. Our protocols are efficient, non-interactive and can be implemented using today's technology. On the technical side, a new uncertainty relation is established

Andrej Bogdanov, Yuval Ishai, Akshayaram Srinivasan