An administrator must preserve a 4 KB master decryption key for at least 25 years in a vault that might outlast current storage hardware. The copy must be readable without specialized equipment, resist electromagnetic-pulse events, and remain usable even if today's storage interfaces become obsolete. Which backup media type BEST meets these requirements?
An LTO-9 magnetic tape cartridge stored in an off-site vault
An offline solid-state drive kept inside a Faraday cage
An encrypted object stored in a long-term cold cloud archive tier
A printed hard copy of the key sealed in a fire-resistant safe
A printed hard copy satisfies all stated constraints because paper can be read with the naked eye, is immune to firmware corruption and EMP, and does not rely on a particular drive or file system that could become obsolete. A magnetic tape cartridge offers long retention but restoring from it requires a compatible tape drive that may not exist decades later. An offline solid-state drive is still subject to bit-rot, controller failure, and EMP damage, and it needs specific interface hardware to read. A cold cloud archive depends on ongoing internet access, provider availability, and server hardware, so it would be unusable if the infrastructure fails or becomes obsolete.