Patent Issues ???
Q: I'm trying to ensure that any encryption algorithms I use in my software development for commercial use is free from any patent issues. I'm a Canadian in Canada developing software to be used internationally. Here's the issue: Suppose I'd like to use the Diffie-Hellman key exchange algorithm (patent 4,200,770) which according to Cylink, the patent holders, is now royalty free for commercial use in the US. If the patent for that algorithm still exists in Canada, can I develop software using the DH key exchange algorithm if the intended target audience is only in the US and be reasonably assured that no patent infringement exists? Further, the concept of having different patents based by Country for the same invention baffles me. Placing a geographic scope on the invention doesn't make sense. I suppose that is another issue entirely. Maybe I'm missing something? I expect that others have come across this issue before, can
A: If a patent is expired, you may make, use and sell the invention disclosed in that patent *in that country.* If there is still a valid Canadian patent, you may not make, use, or sell the invention in Canada, if Canadian law is like US law. You should consult a Canadian patent attorney, and meanwhile assume the worst. Whether there is infringement in coding software in Canada (where it is patented,) to sell it for use in the US, is an interesting question that goes beyond the basics. An attorney would be unwise to give advice without looking at the particular patent, the invention, and a bit of legal research.