Ascii-armor in paper - question

[Daniel Kahn Gillmor]

Hi Egon--

sorry for the delay in responding to you here.

On Mon 2017-12-25 14:49:02 +0100, Egon wrote:
> I have an encrypted GPG Ascii-armored document which I want to print it 
> to paper in short form (if it is possible).
> Does ascii-armor format redundant or redundancy it true only for GPG
> keys?

OpenPGP ASCII-armor does not provide any additional redundancy -- the
"CRC" check at the end of ASCII armor will help you determine if there
was an accidental transcription mistake, but it is *not* capable of
helping you recover from such an error.

ASCII-armor is at its core just base64 encoding.  If you have a binary
document that you want to print to be able to reconstruct byte-for-byte,
you could just as well use the "base64" program to convert it to a
printable sequence.

You don't mention whether your document is OpenPGP-encrypted or
OpenPGP-signed.  I'm assuming in this discussion that the only thing
OpenPGP-related for this document is the ASCII-armoring, since that's
what you mention above, but if there are other OpenPGP characteristics
you care about, you should probably mention them.

> What can I do to print it in "shorter form"? (if available, convert it 
> to some standardized format which produce shorter text).

converting a large document to a smaller document is best done with
compression (e.g. gzip or xz).  You can do this compression before
converting to OpenPGP format, or you can do it as part of the OpenPGP
conversion.  I recommend doing the compression independently of OpenPGP
conversion.

> I want to find a method which help me to reconstruct the printed 
> ascii-armor file from paper more easily (if possible).
>
> Paperkey - I think - working only with GPG keys.

paperkey is specifically designed for OpenPGP keys, correct. It will not
help you produce a more minimal form of the ascii-armored document that
is not an OpenPGP key.

I think what you're looking for is twofold:

 * error correction

 * easy re-digitization


You might find that QR codes attempt to tackle both of these problems.
Take a look at

   https://blog.liw.fi/posts/qr-backup/

for a discussion of that approach, with some pointers.

hope this helps,

    --dkg
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