Question

I’d like to use openssh to sign a file, and then pack

1. the file
2. the public key
3. the signature hash

Into one self-contained file. In a container file like pem. Oh, and I understand that what will be signed and verifiable is the file, not the self-contained thingie.

Answer 1

Yes, I can. All I have to do to is

1. Sign the file
2. Put the public key in the file
3. Put the hash in the file

You can add info like this to all kinds of file types.
Your file can also be an archive itself, in witch case the problem is solved.

To verify the file, first extract (in the proper sense of the term : Read then erase) the hash and the key, then verify.