Printing Keys and using OCR.

Roscoe eocsor at
Tue May 15 08:54:40 CEST 2007

Hey folks,

I'm wanting to store my OpenPGP key on paper, I suspect this is
something someone else has already done. The motivation behind this is
that paper is the most stable backup medium I have.

I have tried printing out a key, then scanning and using gocr on the result.
That was unsuccessful due to the high number of errors in the OCR
phase, I suspect with a carefully selected font and font size I could
sigificantly cut down on that error rate.

Now since even a 99.99% accuracy in the OCR phase is still going to
cause a large headache when you're trying to track down what one or
few characters got interpreted wrong amongst a screenfull of them, I
thought some error correction would be a very good idea.
(First thing that came to mind was par2+base64 but I think this might
have have a few issues.).

Then came the realisation that printing out english letters was a
woefully inefficent way to store binary data on a piece of paper. I'm
certain there must be more compact and robust ways (ie: without subtly
similar symbols like 0 and O) way to store information.

So...Does anyone :

Know of a system that can take binary data and output an image to be
printed out, that is then capable of extracting that binary data from
an imperfect scan of the image.

OR Have any success stories regarding printing, scanning then OCRing
keys or any other data?
If so how did you do it? (what did you use for error correction, what
font, what size etc..)

(Oh, and I'm aiming to do this with just Free/Open software.)

-- Roscoe

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