paper and pencil cyrptography

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phillip1882
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paper and pencil cyrptography

Postby phillip1882 » Mon Jul 01, 2019 12:07 am UTC

inspired by bitcoin, i was interested to see if you could create a paper pencil crypto currency
like, have a box of dice, shake, and this is your public key, add 12 more dice, shake and this is your private key.
good luck have fun

Tub
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Re: paper and pencil cyrptography

Postby Tub » Mon Jul 01, 2019 11:38 am UTC

You can easily do pubkey cryptography with a pen, paper and a couple of dice. Just look into existing schemes like RSA or elliptic curves. It just takes forever.

For example, RSA recommends at least 2048-bit keys. If you have a reasonably short message (about a tweet full), encryption or decryption requires you to do around 3000 multiplications on 600-digit integers.

You can reduce key lengths until its feasible to do it on paper, but then your communication will be easily broken by anyone with a computer.

/edit: pubkey cryptography doesn't equal bitcoin though. Crypto-mining on paper is bound to be inefficient.

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phillip1882
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Re: paper and pencil cyrptography

Postby phillip1882 » Sun Jul 07, 2019 7:47 pm UTC

right, there are several hurdles to over come for pencil paper crypto currency.
how would the currency itself be generated?
how would you trade coins without giving away your private key?
how would you make it such that doing it with a computer isn't significantly more efficient?
(the third one might not be too much of an issue, it doesn't or at least it shouldn't matter
how the coins are traded, as long as doing it with paper and pencil isn't too difficult)
good luck have fun

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Re: paper and pencil cyrptography

Postby Xanthir » Mon Jul 08, 2019 11:11 pm UTC

From your posts, it sounds like you don't have a great starting knowledge of public-key crypto, right? It's a pretty interesting subset of applied math; I recommend reading up on it!

(I ask because your original post gave an example of public+private keys being generated randomly; in reality there's randomness involved in their generation, but the two numbers are intimately related and *not* random relative to each other.)

But yeah, mostly what Tub said. Anything relying on crypto can be done by hand, it will just be vastly slower than working on a computer, because it's all just A Lot Of Arithmetic when you get down to it. There's no shortcuts here.

Btw, the mechanics of a cryptocurrency are kinda interesting to read up on, too. Bitcoin, at least, is surprisingly simple to understand the basic details of. I don't recommend *doing anything* with a cryptocurrency, tho, as every single one of them is a terrible hack and most are nakedly pyramid schemes.
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