diff --git a/unit04_public_key/README.md b/unit04_public_key/README.md
index b4d0b09..400fe7c 100644
--- a/unit04_public_key/README.md
+++ b/unit04_public_key/README.md
@@ -18,9 +18,9 @@ The key concepts are: Basics, RSA, Elliptic Curve and ElGamal.
 ## Presentations
 
 * Week 4 Presentation (PDF) - Public Key Encryption: [here](https://github.com/billbuchanan/appliedcrypto/blob/master/unit04_public_key/lecture/chapter04_public_msc.pdf).
-* Week 4 Presentation (video) - Public Key Encryption: [here](https://youtu.be/QEYqkxuzoTg).
+* Week 4 Presentation (video) - Public Key Encryption: [here](https://youtu.be/qoRCL3qDnXE).
 * Week 4 Doodle (video) - Public Key Encryption: [here](https://youtu.be/0zArGECThXI).
-<!-- * Week 4 Presentation (lecture video - 8 Feb 2020) - Public Key Encryption: [here](https://www.youtube.com/watch?v=PEdCHWdE3zk). -->
+
 
 ## Lab