On the quadratic reciprocity law

In the number theory, the law of quadratic reciprocity is a theorem about modular arithmetic that gives conditions for the solvability of quadratic equations modulo prime numbers. It noticed by Euler and Legendre and proved by Gauss. In this paper, we will study the quadratic reciprocity law theorem where the Euler Criterion and Legendre Symbol are involved. The application of quadratic reciprocity law theorem is given in cryptography, where the Quadratic Residuosity Problem considered as a hard mathematical problem for Goldwasser Micali Randomized Public Key Cryptosystem. This system will be discussed with the details in this paper.