International Data Encryption AlgorithmRFC 3058 [CMS], [S/MIME]でのIDEA暗号化アルゴリズムの利用https://tex2e.github.io/rfc-translater/html/rfc3058.htmlTLS 1.1RFC 5469 DES and IDEA Cipher Suites for Transport Layer Security (TLS)で非推奨 → 8996