Reply to post: Re: Just wondering

Microsoft planning blockchain-as-a-service for Azure apps


Re: Just wondering

The falsification conditions come up as a result of the way that blockchain works. Basically, as the name suggests, this is a public ledger with the use of mutual digital signatures to agree transactions. The problem comes in the way that the blocks themselves are managed. I am going to simplify, largely because although I read through it in detail, that was a while ago and I am not confident of my ability to relate the key points accurately.

When you have large numbers of disparate parties all attempting to append a transaction to the same block in a chain, you are going to get scenarios where there are atomic failures at the transaction level. For example, suppose there is one free slot in a block and two or more parties try and use it. Only one will succeed and the others will fail. The entire blockchain is designed to handle this using a mechanism analogous to the 2-stage commit of XA-comliant systems... However, it does this, at least in part, by allowing splitting of blockchains and downstream conflict resolution of scenarios such as the one I described above.

But what happens if you and I have a transaction thrown out and then, we it's time to re-submit, I decline? This is [as I understood it from the read-through] an extremely narrow scenario that is virtually impossible to predict in advance. When all the potential conflicts and block splits are resolved and confirmed into the chain, then a transaction is deemed "guaranteed". However, there exists a narrow window of time between when the transaction is written to the block and when it is fully committed, in which another user/transaction source could challenge/trump that commit and force a do-over.

I think that's the "almost impervious to falsification" bit, if I understand it correctly...

For what it's worth, people are predicting that we need to change the underlying architecture of Bitcoin because the collision scenario I describe will only get more prevalent as more people use it. There appears to be something of a tussle underway in the BC community on this very point...

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