Update free-courses-en.md

free-courses-en.md

@@ -108,6 +108,7 @@
 * [MIT´s Mathematics for Computer Science](http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-042j-mathematics-for-computer-science-fall-2010/video-lectures/)
 * [MIT´s Introduction to Algorithms](http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-006-introduction-to-algorithms-fall-2011/)
 * [Stanford Cryptography I](https://www.coursera.org/course/crypto)
+* [Stanford Cryptography II](https://www.coursera.org/course/crypto2)
 
 
 ### OCaml