Implementation of Diffie-Hellman algorithm of key exchange

Contents

  1. Introduction
  2. Diffie–Hellman algorithm of key exchange
        1. Description of the algorithm
        2. Brief survey of some existing implementations
  3. C++ library, which implements the algorithm
        1. Class ULong of long integer with the arbitrary dimension
        2. Implementation of Diffie – Hellman algorithm
        3. Illustration of library usage with an example
  4. Structure of project files

1. Introduction

The article is devoted to the development of the library that implements the Diffie – Hellman cryptographic algorithm of key exchange. The library appeared as a result of the necessity to use the Diffie – Hellman algorithm without the involvement of any third-party libraries.
2. Diffie – Hellman algorithm of key exchange
2.1 Description of the algorithm

Diffie – Hellman algorithm is an algorithm that allows two parties to get the shared secret key using the communication channel, which is not protected from the interception but is protected from modification.

Diffie – Hellman algorithm is extremely simple in its idea and with it has rather high level of cryptographic stability, which is based on the supposed complexity of the discrete problem of taking the logarithm.

Supposing there are two participants of the exchange (let’s call them Alice and Bob, as it is traditionally established in cryptography). Both of them know two numbers P and G. These numbers are not secret and can be known to anyone. The goal of Alice and Bob is to obtain the shared secret key to help them to exchange messages in future.

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