Thank you for the article. I was not aware of that article. My first implementation was done in 1997 or 1998. I am involve in computer security for three decades and I was familiar with Feistel networks. I am not a cryptographer but I have reverse engineered algorithms using this structure. Never checked patents because I think this is a natural construction and I always wondered why there were no other public ideas around this problem. This is not the first time it happened to me.