Key archival...

Paperkey is the "best" archival method known to me..

Are there any better methods.

Ideally I would like to have a business card size CD-RW or
DVD-RW or BD-RE... I can only find CD-R, and I bet none of these are archival quality...

I believe even the smart card or USB key may not be safe as the data is stored electronically (electrons in floating gates), they may get erased over time or by water etc...

Ghat