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Author Topic: What will happen if a block hash= trans hash?  (Read 288 times)
girlbtc.com
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December 08, 2016, 08:35:06 AM
 #1

When you search the hash in blockchain.info

It will give you Error?  or Both?

And same question , what if two trans has same hash? will it be confused by the bitcoin-core or the miners.


For example:
The hash of Trans A and Trans B is the same.
You have valid output in trans A,
But the bitcoin-core find the Trans B and judge you as invalid Smiley

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December 08, 2016, 09:07:29 AM
 #2

When you search the hash in blockchain.info

It will give you Error?  or Both?
To my knowledge, this is very very rare and I believe its close to impossible. I need clarifications on this however, can someone else help to answer this question?
And same question , what if two trans has same hash? will it be confused by the bitcoin-core or the miners.
This has happened before. We need to understand how transaction hash works to know how it is impossible now.

A transaction hash consist of a double SHA256 hash of the following (in order):
1. A 32-bit version number.
2. inputs used in the transaction
3. outputs and the criteria for spending it
4. 32-bit nlocktime

So, for the transaction IDs to be identical, they must have the exact of the above.

This is only possible if a collision is found or in coinbase transactions(used to be easy).

BIP30 solved the coinbase TXID conflict implications by preventing miners from including any TX that has the same TXID from a previous block and has outputs unspent.[1] BIP34 makes the duplicate coinbase transactions even harder to create by adding block number into coinbase.

[1] https://github.com/bitcoin/bips/blob/master/bip-0030.mediawiki


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December 09, 2016, 05:53:27 AM
 #3

Its very rare for two random strings to have same hash

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