Vintage Bit Cryptography

Abstract

We propose to use a Random High-Rate Binary (RHRB) stream for the purpose of key distribution. The idea is as follows. Assume availability of a high-rate (terabits per second) broadcaster sending random content. Members of the key group (e.g. {Alice, Bob}) share a weak secret (at least 60 bits) and use it to make a selection of bits from the RHRB stream at an extremely low rate (1 bit out of 10¹⁶ to 10¹⁸). By the time that a strong key of reasonable size has been collected (1,000 bits), an enormous amount of data has been broadcast (10¹⁹ − 10²¹ bits). This is 10⁶ to 10⁸ times current hard drive capacity, which makes it infeasible for the interceptor (Eve) to store the stream for subsequent cryptanalysis, which is what the interceptor would have to do in the absence of the shared secret. Alternatively Eve could record the selection of bits that correspond to every value of the weak shared secret, which under the above assumptions requires the same or greater amount of storage i.e. 2⁶⁰×10³. The members of the key group have no need to capture the whole stream, but store only the tiny part of it that is the key. Effectively this allows a pseudo-random sequence generated from a weak key to be leveraged up into a strong genuinely random key.