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Date: Mon, 27 Jul 2015 15:46:37 -0400
From: John Tromp <>
To: Bill Cox <>
Cc: "" <>, 
	"" <>
Subject: Re: [Cryptography] [OT] Improvement to Momentum PoW

On Mon, Jul 27, 2015 at 2:29 PM, Bill Cox <> wrote:
> A problem with Momentum as currently implemented is that it can be run with
> reduced memory, enabling efficient GPU attacks.

Dave Andersen's latest remarks on his GPU code:
You can ask him what he thinks is a faster implementation.

Fore reduced memory, you can find all collisions in 8MB,
using Cuckoo Cycle's algorithm for finding 2 cycles in bipartite graphs.

>  I think we can get around
> this problem simply by changing the parameters it uses.

> If instead, we run with n == 26, and Hb's output also being 26 bits, then we
> get around 2^26 collisions.

To me, that's a completely different beast.
I would no longer call that Momentum...


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