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

[Daniel Kahn Gillmor]

Hi Bjoern--

On Thu 2017-05-18 19:01:25 +0200, Bjoern wrote:
> Okay, I figured out how to get the correct public key part.
>
> Now, I am a little bit confused about which data are really required
> in the public key.
>
> The key eg. returned by the Autocrypt bot contains the following
> packets (from https://tools.ietf.org/html/rfc4880)
>
> Public-key Packet -- 272 bytes raw
> User ID Packet --  28 bytes raw, contains `bot123 <bot at autocrypt.org>`
> Signature packet -- 343 byte raw
> .... more packets
>
> All in all about 3,7 KB of data. I'm no expert, but for the pure
> encryption, only the first packet is required? What is expected by the
> Autocrypt-standard.

I think you're looking for this information:

    https://autocrypt.org/en/latest/level0.html#type-p-openpgp-based-key-data

In particular, the expected key should be a series of 5 OpenPGP packets:

       * a signing-capable primary key Kp
       * a user id
       * a self signature
       * an encryption-capable subkey Ke
       * a binding signature over Ke by Kp


is that what you're looking for?

   --dkg
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