noun
book cipher; Ottendorf cipher
A cipher where each plaintext letter is encoded by a book, page, line, and word position. Used in classical cryptography.
書籍暗号は、あらかじめ決めた本の特定の単語を参照して暗号化する方法だ。
A book cipher is a method of encryption that refers to specific words in a prearranged book.
Compound of 書籍 (book) and 暗号 (cipher). A straightforward technical term.