diff --git a/courses/free-courses-en.md b/courses/free-courses-en.md
index bf149038e..ae4acfb41 100644
--- a/courses/free-courses-en.md
+++ b/courses/free-courses-en.md
@@ -508,7 +508,6 @@
 * [Cryptography & Network Security](https://www.youtube.com/playlist?list=PLBlnK6fEyqRgJU3EsOYDTW7m6SUmW6kII) - Neso Academy
 * [Cryptography Lecture Series](https://www.youtube.com/playlist?list=PL2jrku-ebl3H50FiEPr4erSJiJHURM9BX) - Christof Paar
 * [Foundations of Cryptography](https://www.youtube.com/playlist?list=PLgMDNELGJ1CbdGLyn7OrVAP-IKg-0q2U2) - NPTEL  Indian Institute of Science, Bengaluru
-* [Introduction to Cryptography](https://open.ruhr-uni-bochum.de/en/lernangebot/introduction-cryptography) (Christof Paar)
 * [Stanford Cryptography I](https://www.coursera.org/course/crypto) - Dan Boneh