Store to tape.
Verify the store operation by restoring it elsewhere.
Delete both the original and the restored verify copy.
Put the tape in a moisture heat resistant container.
Dig a hole.
Bury it somewhere.
That’s what tapes are for, entropy is nil.
Some backup software even has encryption. If so, you’d also need a key to restore the tape.
It would be like the moneybox near the tree in a field in “Shawshank Redemption”.