keep it in bank safety deposit box.
Keep the original in a binder with sleeves, in a bank locker. Also, make a clear color copy and keep it at home in a file cabin. At the same time, make a clear, color scan to PDF file and put it in a palm size external drive that you can carry with you on trips. That's what I did.
I have all my immigration documents inside a 3 ring binder, inside vinyl sleeves, and the binder is safely inside a bank safe deposit box.
I would definitely make copies of the Natz certificate and keep them separate, in the event of an earthquake or sinkhole swallows the bank!
Can we do this? Is it not illegal? I like this idea of scanning it and storing it in a flash drive........ But remember, you should never ever lose it.......
Well, if this gives you headache, then your house must be stuffed with Tylenol or Advil by now because there are more important things in life to worry about. My certificate is lying in the drawer in my house - do I worry that my house might burn down? Yes, but losing the certificate will be the least harmful side effectBut it is extremely difficult to choose the best way to preserve the NTZ cert. Another headache comes.
Laminate your Natz certificate with the heated laminating plastic using a heat laminator. All my documents are laminated that way ( except SS card). It protects your documents forever.
Laminating the Certificate of Naturalisation renders it invalid. Nobody will accept the laminated NC - you can as well put it in the garbage. I think the USCIS officials at the naturalisation ceremony should stress more about it.