improve key and signature interop

[n8fr8]

The way ProofMode does keys and signatures is difficult to handle in crypto libraries other than gpg At least in my experience. Pycryptodome couldn't read the key Is there a happy medium where the format could be understood by both gpg and most crypto libraries?

[n8fr8]

test with: https://pypi.org/project/python-gnupg/ and https://pycryptodome.readthedocs.io/en/latest/