Most of the current public key cryptosystems’ security is based on the integer factorization and the discrete logarithm, which are mathematical problems that are considered difficult to solve. However, the publication in 1994 of the Shor’s algorithm [1] was a major setback for the world of cryptography, since it provided a quantum algorithm capable of solving efficiently these mathematical problems. Therefore, in recent years many governments and technology companies have put a lot of effort into developing what is known as post-quantum cryptography, i.e. the science that studies cryptosystems that are resistant to quantum attacks. Along these lines, in 2016 the National Institute of Standards & Technology launched a competition with the aim of establishing and standardising the best performing post-quantum cryptosystems, being the NTRU (Nth Degree Truncated polynomial Ring Units) cryptosystem one of the candidates still on the table. The aim of this project is to study the quantum-resistant cryptosystem NTRU, both from a theoretical and practical point of view. Firstly, the mathematical results on which it is based are presented and the existing attacks against it are analyzed. Finally, a practical implementation of the cryptosystem and four of its attack is carried out, from which experimental results are extracted.