# Possible to recreate GPG using pen and paper?

Harry Rickards hrickards at l33tmyst.com
Sat Jun 6 10:42:22 CEST 2009

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On 06/05/09 21:21, Andre Amorim wrote:
> game ? theory?
> or
> ?
>
> 2009/6/5 Harry Rickards <hrickards at l33tmyst.com>:
> On 06/05/09 19:46, David Shaw wrote:
>>>> 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
> Thanks for the link, I'll have a read through it (although it might take
> a while - 28k words). When you say understand the algorithm, do you mean
> understand that you take two prime numbers, and multiply them together
> to get n, and then multiply them together using the totient function
> etc, or understand *why* you take multiply them together using the
> totient function etc?
>

Maths project on breaking codes. Thought I might as well encrypt some
stuff in hard-to-break ciphers like the ones GPG use as well. Plus it'll
be fun.

- --
Many thanks
Harry Rickards (GPG Key ID:646ED06A)

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