[1] Safari Dev Center: Safari HTML Reference: Supported Attributes (2010-03-20 17:49:52 +09:00 版) http://developer.apple.com/safari/library/documentation/AppleApplications/Reference/SafariHTMLRef/Articles/Attributes.html#//apple_ref/doc/uid/TP40008058-keytype

[2] Remove <keygen> (domenic著, 2017-01-14 07:03:02 +09:00) https://github.com/whatwg/html/commit/5baa38720f6e83c94a50018c4565808ad548d69c