🚀 go-pugleaf

I have found that a simple way to do this to use Adobe Illustrator and
input your signature as a series of splines. My signature results in
approximately 80 curves - each curve consists of 6 coords with roughly
6 digits of precision. As simply method of protecting this is to only
include a version of this in documents which has been modified to
encode the date+time+documentID (you are of course free to encrypt
this "timestamp" before encoding it into the coords). The result is
that if someone edits the PostScript into another document you can
establish if it is the correct signature for this document [you can
even write a procedure to do signature authentication if you wish to
use public key encryption techniques]. The nice thing is that small
perterbations to the signture when printed (due to the modification of
the low order digits in the coords) does not destroy the appearance of
the signature. A homework problem is to determine the range of
variance which produces an observable but not objectionable change
when the document is printed at a given resolution. A more advanced
homework problem is to produce a version that when scanned (after
being printed) will permit the extraction of the encoded information -
thus making it possible to authenticate printed versions without access
to the source PostScript. [For the real security enthusiast you can
also very the line used for the spline to ensure that you can tell an
original printed version from a copy of a printed version (using the
same techniques used for high security printed documents {which take
advantage of the physics of toners}).]
Chip