Cryptography RSA private key calculation

This video demonstrate how to determine the private key with a simplified RSA algorithm. Given p, q, e it explain how to determine the private key for the decryption of the message. e can be any value that is coprime with PHI. In this exemple the numbers are really smalls but in the reality the algorithm use much longer numbers. During the calculations the The Euclidean Algorithm it's used. You can find more informations about it here: https://www.khanacademy.org/computing/computer-science/cryptography/modarithmetic/a/the-euclidean-algorithm You can confirm the calculation with this webtool: https://www.wolframalpha.com/widgets/view.jsp?id=d5bb63088eb2fb2e762f1c260d2b886d