Tight security proofs for the bounded-storage model
Stefan Dziembowski, Ueli M. Maurer · 2002
In the bounded-storage model for information-theoretically secure encryption and key-agreement one can prove the security of a cipher based on the sole assumption that the adversary's storage capacity is bounded, say by s bits, even if her computational power is unlimited. Assume that a random t-bit string R is either publicly available (e.g. the signal of a deep space radio source) or broadcast by one of the legitimate parties. If s < t, the adversary can store only partial information about R. The legitimate sender Alice and receiver Bob, sharing a short secret key K initially, can therefore potentially generate a very long n-bit one-time pad X with n jKj about which the adversary has essentially no information, thus at rst glance apparently contradicting Shannon's bound on the key size of a perfect cipher.