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From: Eric Voskuil <eric@voskuil.org>
To: Alex Morcos <morcos@gmail.com>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>
Cc: Thomas Kerin <me@thomaskerin.io>
Subject: Re: [bitcoin-dev] [BIP Proposal] Buried Deployments
Date: Wed, 16 Nov 2016 17:41:51 -0800	[thread overview]
Message-ID: <6b3837bb-cde9-87e9-5822-5405a6f7e2f7@voskuil.org> (raw)
In-Reply-To: <CAPWm=eWcZZCzKWXkX=sD=cnjTCEGmdN3G_hf85rwy60EAUXUqQ@mail.gmail.com>

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On 11/16/2016 05:24 PM, Alex Morcos wrote:
> huh?
> can you give an example of how a duplicate transaction hash (in the same
> chain) can happen given BIP34?

"The pigeonhole principle arises in computer science. For example,
collisions are inevitable in a hash table because the number of possible
keys exceeds the number of indices in the array. A hashing algorithm, no
matter how clever, cannot avoid these collisions."

https://en.wikipedia.org/wiki/Pigeonhole_principle

e

> On Wed, Nov 16, 2016 at 7:00 PM, Eric Voskuil via bitcoin-dev wrote:
> 
>     On 11/16/2016 03:58 PM, Jorge Timón via bitcoin-dev wrote:
>     > On Wed, Nov 16, 2016 at 3:18 PM, Thomas Kerin via bitcoin-dev
>     > <bitcoin-dev@lists.linuxfoundation.org
>     <mailto:bitcoin-dev@lists.linuxfoundation.org>> wrote:
>     >> BIP30 actually was given similar treatment after a reasonable amount of time
>     >> had passed.
>     >> https://github.com/bitcoin/bitcoin/blob/master/src/main.cpp#L2392
>     <https://github.com/bitcoin/bitcoin/blob/master/src/main.cpp#L2392>
>     >
>     > This is not really the same. BIP30 is not validated after BIP34 is
>     > active because blocks complying with BIP34 will always necessarily
>     > comply with BIP30 (ie coinbases cannot be duplicated after they
>     > include the block height).
> 
>     This is a misinterpretation of BIP30. Duplicate transaction hashes can
>     and will happen and are perfectly valid in Bitcoin. BIP34 does not
>     prevent this.
> 
>     e


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  reply	other threads:[~2016-11-17  1:41 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-11-14 18:17 [bitcoin-dev] [BIP Proposal] Buried Deployments Suhas Daftuar
2016-11-14 18:47 ` Eric Voskuil
2016-11-15 14:42   ` Suhas Daftuar
2016-11-15 17:45   ` Btc Drak
2016-11-15 22:42     ` Eric Voskuil
2016-11-16 13:29       ` Jameson Lopp
2016-11-16 13:58         ` Eric Voskuil
2016-11-16 14:18           ` Tier Nolan
2016-11-16 14:32             ` Alex Morcos
2016-11-16 21:01               ` Peter Todd
2016-11-16 22:21                 ` Eric Voskuil
2016-11-17  3:06                 ` Luke Dashjr
2016-11-16 14:18           ` Thomas Kerin
2016-11-16 23:58             ` Jorge Timón
2016-11-17  0:00               ` Eric Voskuil
2016-11-17  1:24                 ` Alex Morcos
2016-11-17  1:41                   ` Eric Voskuil [this message]
2016-11-17  0:13             ` Eric Voskuil
2016-11-16 23:48           ` Jorge Timón
2016-11-17  1:50           ` Pieter Wuille
2016-11-17  2:16             ` Eric Voskuil
2016-11-17  2:47               ` Pieter Wuille
2016-11-17 10:10                 ` Eric Voskuil
2016-11-16 14:38   ` Tom Zander

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