Carrying it on your person was not a listed req in the challenge... and if you are carrying on person all the time it basically removes the worry about what media/format/encryption to use because the obvious answer is whatever is most current and since your carrying it on you you keep updating media/format/encryption every cpl years.
I'd argue though that on person is not a secure backup... its an offline working copy. If its on you then it can be seized if you are, damaged / destroyed if you are, etc.
The challenge as it was written made this sound like an archived long term thing which is why my original reply.
