The article in Japanese, 昔の特許文献の探し方と戦前の暗号関係の特許（付：戦前の中間処理実例）, describes pre-WWII Japanese patents related to cryptography. My guides to search for patents in J-PlatPat, the database of the Japan Patent Office, was outdated since a major reconstruction of the JPO website in May 2019. Now, I updated the descriptions to reflect the changes.
