In much of modern cryptography, for many cryptographic tasks, the security of protocols that
have been designed is based on the intractability of a problem such as factorization of
randomly chosen large numbers. To date, the problems assumed to be intractable all have
the same form; they are based on a one-way function, ie one that is easy to compute but
hard to invert. In fact, intuitively, any protocol that is secure needs to be based on some
notion of “one-wayness”, although perhaps not with respect to the sarne definition of “one …