The mathematical area of integer factorization has gone a long way since the early days of Pierre de Fermat, and with simpler algorithms developed in the last century such as the Trial division and Pollards rho algorithm to the more complex method of the Quadratic sieve algorithm (QS), we have now arrived at the General Number Field Sieve (GNFS) which has been recognized as the fastest integer factorization algorithm for very large numbers. Today the research of integer factorization has many applications, among others in the security systems of encryption methods like the famous RSA algorithm. In this thesis I will describe and give calculated examples of the various integer factorization methods mentioned. I will also make a comparison of...