Bitcoin Forum

When people are saying that we can use the blockchain technology to either store or just verify documents, do they mean the bitcoin blockchain or is it just the idea behind the bitcoin blockchain  (https://mindmajix.com/the-theory-of-blockchain-explained)that could be utilized in other blockchains?

I have found https://www.proofofexistence.com/ which creates a transaction with a hashed value of a document which can then be verified. I think it's a good idea, but isn't it spam in the bitcoin block chain? Shouldn't there be a separate blockchain for document verification, so the bitcoin blockchain can be only about transferring money?

The Ethereum blockchain is used quite often for storing identity data, school certificates, document verification, anticounterfeiting etc etc.
There are many ICOs and projects focusing on the above areas of interest. I am not familiar with any projects that do this on the Bitcoin blockchain though.   

You can always use op_return to store data in the blockchain without increasing the utxo set: https://en.bitcoin.it/wiki/OP_RETURN
But like Pmalek already suggested: other blockchain implementations (like ethereum) are better suited to store data...

https://etherscan.io/tx/0x2d6a7b0f6adeff38423d4c62cd8b6ccb708ddad85da5d3d06756ad4d8a04a6a2 (click on view input => UTF-8), source: https://cryptobulls.info/chinese-student-censorship-ethereum

While any one can embed data in a transaction using op_return and miners are validating these transactions in ordre to collect fees, there is not much you can do to stop it.

In fact, you can find some funny data stored in blockchain: here (http://www.righto.com/2014/02/ascii-bernanke-wikileaks-photographs.html?m=1)

There is not difference between what these people do and what proofofexistence.com do except that for the last one it is an intentional spam and you are not really saving files but a hash that proves you had the file at a that moment.

Storj and other blockchain based solutions are better when it comes to store files but you have to know that your data is not saved on their blockchains.

Why it would be spam? You are utilizing blockchain for which it has been invented. Through this process, one can register a file in bitcoin blockchain, blockchain only store the hashes of this file. Using bitcoin blockchain is the best since it is the most active.
I might have some lacking because I never utilized this for any coin but DeepOnion. I have used DeepVault (https://deepvaultonline.com/) from DeepOnion. For your info, DeepOnion Blockchain Is Guaranteed By The Bitcoin Blockchain (https://deeponion.org/community/threads/technical-aspect-on-how-deeponion-blockchain-is-guaranteed-by-the-bitcoin-blockchain.37940/#post-614238).

You pay so that full nodes stock this data forever, so it is not spam. However it could be seen as inappropriate.

Why the Bitcoin block chain is used is because it is the one with the more chainwork (https://bitcoin.stackexchange.com/questions/26869/what-is-chainwork), which makes it the most unlikely to change.

The block chain has been designed to order transactions.

If you are talking about companies not related to cryptocurrencies then you are mostly talking about their own version of Blockchain technology, which means that they don't completely use the one that Bitcoin is in. That is why you are seeing news like Walmart (https://cointelegraph.com/news/walmart-awarded-patent-for-blockchain-based-medical-records-system) securing a patent on their own version of Blockchain specialized for medical records. Other companies like IBM, Bank of America, and Alibaba have their own patented versions of Blockchain some of them even have more than one patented version of it.

That depends since both of them are possible, but on most cases people are talking about it's application on another blockchain. But beware that most them are using "blockchain" term as buzzword and actually they're using distributed database.


You can store the file on another blockchain/side-chain, so people who wish to obtain data just need bitcoin transaction id/hash and see it's OP_RETURN data. I'm pretty sure another cryptocurrency/blockchain have similar feature, although i can't remember it.

As already mentioned before, DeepOnion has this feature and well working webservice for this. DeepOnion Hybrid pos+pow blockchain very secured and you no need to worry about changing data in blockchain and pay expensive BTC tx fees for every registered file.
Here is well explained video about this technology

https://www.youtube.com/watch?v=r1dN0xYMZmU

Why bitcoin specifically? You can use the ETH blockchain for this. Projects are already utilizing it.

It is considered spam because bitcoin was not exactly designed for fingerprinting document. The hash capability is needed for bitcoin to work and this capability came as a side effect, also thanks to built in Script.

Ethereum is much better suited arguably because it sells itself as a decentralized computing platform. Turing complete makes it easy to implement it as well over bitcoin scripting.

At the end the way blockchain works allow you to hash any sort of data and store them into proven history.

IPFS may be an interesting evolution of this. Hashing is native to the location of the file, and the file itself is stored in a distributed manner.

They simply calculate the hash for the entire DeepOnion blockchain and register it in the Bitcoin blockchain by including the hash in a bitcoin transaction.
As far as I know, the registration of the hash in the Bitcoin blockchain is done every month.

Hi,

With regards to storing harmful and potentially illegal data in the bitcoin blockchain, do check out our work on Redactability in public blockchains that's explained in this (https://bitcointalk.org/index.php?topic=5102449.0) thread.

Cheers!