[Autocrypt] How to create the "raw key" part from an RSA key

[Vincent Breitmoser]

> fwiw, "armor" in OpenPGP land usually refers to the base64-encoding in
> addition to the "-----BEGIN…" and "-----END…" lines and the headers.

For completenes' sake: it also includes the crc checksum. Although that
is largely ignored by implementations, since there is not really
anything useful that can be done if it doesn't check out. I think it was
introduced when methods of data transfer were less reliable, so it's
largely a historical artifact at this point.

(for reference: https://tools.ietf.org/html/rfc4880#section-6.2)

 - V