# A blockchain-based voting platform

I am working on designing an open source blockchain-based voting platform. Looking for feedback and advice / AMA

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Maxime Suard
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Fri 25 Jan 2019 11:24AM

Public Gitlab repos (mostly empty for now): https://gitlab.com/echo-protocol

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Josh Fairhead
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Sat 26 Jan 2019 8:44PM

@willabramson This might be interesting to your lot ;)

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Will Abramson
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Mon 28 Jan 2019 10:39AM

Thanks, it makes for an interesting read. Will share with the lab. I am wondering why the cryptosystem wants to be multiplicative homomorphic rather than additive. What am I missing here?

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Maxime Suard
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Thu 31 Jan 2019 4:09PM

Hey Will, thanks!

With a multiplicative homomorphic crypto system you can conduct votes with an unlimited amount of choices each represented by a prime number.

Ballots are encrypted and aggregated by multiplying the encryption ciphertexts.

Once the vote ends you can decrypt the aggregate and you get the product of all un-encrypted ballots.

You can then obtain the individual scores of each choices by computing the prime numbers decomposition of this decrypted aggregate.

So the multiplicative homomorphy takes advantage of the fact that any integer can be uniquely decomposed as a product of prime numbers.

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Josh Fairhead
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Fri 8 Feb 2019 9:00AM

I nearly understand this :p

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Will Abramson
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Sat 2 Feb 2019 11:46AM

Ah I see, so the number of votes for each item is determined by the power to which the prime number that represents that item is raised?

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Maxime Suard
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Sat 2 Feb 2019 11:55AM

yep :)

Josh Fairhead· Sat 5 Jan 2019 8:28PMThis is quite interesting in signalling preferences: https://colony.io/budgetbox.pdf?mc_cid=2887bf737e&mc_eid=494078b35d