Possible to recreate GPG using pen and paper?

[David Shaw]

On Jun 5, 2009, at 2:52 AM, Harry Rickards wrote:

>
> Would it be possible to do the same job that GPG does (using all the  
> same algorithms) simply using a pen and paper? You can do simple  
> public key crypto with RSA, by choosing two primes and doing a  
> multitude of stuff with them. I understand that it will take a while  
> to actually encrypt/decrypt something, and you'll need a calculator  
> as well, but it would be fun to try all the same.

It is definitely possible.  It might take a while and use a good bit  
of paper, but it's possible.  You would need to understand the public  
key algorithm (RSA, for example) as well as the symmetric cipher  
(3DES, AES, etc).  The actual bytes-in-a-row format is specified in  
RFC-4880 (http://www.ietf.org/rfc/rfc4880.txt)

David