With respect, you really shouldn't be designing your own cryptographic protocols if they are going into a product. Even the best of the best make serious mistakes. A course is not going to give you the confidence that you need. There are so many peer reviewed protocols out there that there's almost no need to make one yourself unless you're in a very specialised or niche scenario. That said, if you just want to learn about them, there are plenty of good, readable books like Real World Cryptography and Applied Cryptography (Schneier).