A One-way function is an invertible function that is
easy to compute, but whose inverse is difficult to compute.
Secure PKCs are built using one-way functions that have a
*trapdoor. The trapdoor is a piece of auxiliary
information that allows the inverse to be easily computed.
The Discrete Logarithm
Problem
Definition Let be a primitive root for and let be a nonzero element of . The Discrete
Logarithm Problem (DLP) is the problem of finding an
exponent such that
The number is called the
discrete logarithm of to the base and is denoted by .
Definition Let be a group whose group law we denote by
the symbol . The
Discrete Logarithm Problem for is to determine, for any two given
elements and in , an integer satisfying
Diffie-Hellman Key Exchange
Diffie-Hellman Key Exchange
Definition. Let be a prime number and an integer. The (DHP) is
the problem of computing the value of from the known
values of and
.
